Remove xerrors dependency

Closes #134

Author: nhooyr

README.md

@@ -32,7 +32,7 @@ go get nhooyr.io/[email protected]
 
 For a production quality example that shows off the full API, see the [echo example on the godoc](https://godoc.org/nhooyr.io/websocket#example-package--Echo). On github, the example is at [example_echo_test.go](./example_echo_test.go).
 
-Please use the [golang.org/x/xerrors.As](https://godoc.org/golang.org/x/xerrors#As) package to check for [websocket.CloseError](https://godoc.org/nhooyr.io/websocket#CloseError). See the [CloseError godoc example](https://godoc.org/nhooyr.io/websocket#example-CloseError).
+Please use the [errors.As](https://golang.org/pkg/errors/#As) function [new in Go 1.13](https://golang.org/doc/go1.13#error_wrapping) to check for [websocket.CloseError](https://godoc.org/nhooyr.io/websocket#CloseError). See the [CloseError godoc example](https://godoc.org/nhooyr.io/websocket#example-CloseError).
 
 ### Server
 

accept.go

@@ -4,13 +4,13 @@ import (
 	"bytes"
 	"crypto/sha1"
 	"encoding/base64"
+	"errors"
+	"fmt"
 	"io"
 	"net/http"
 	"net/textproto"
 	"net/url"
 	"strings"
-
-	"golang.org/x/xerrors"
 )
 
 // AcceptOptions represents the options available to pass to Accept.
@@ -42,31 +42,31 @@ type AcceptOptions struct {
 
 func verifyClientRequest(w http.ResponseWriter, r *http.Request) error {
 	if !headerValuesContainsToken(r.Header, "Connection", "Upgrade") {
-		err := xerrors.Errorf("websocket protocol violation: Connection header %q does not contain Upgrade", r.Header.Get("Connection"))
+		err := fmt.Errorf("websocket protocol violation: Connection header %q does not contain Upgrade", r.Header.Get("Connection"))
 		http.Error(w, err.Error(), http.StatusBadRequest)
 		return err
 	}
 
 	if !headerValuesContainsToken(r.Header, "Upgrade", "WebSocket") {
-		err := xerrors.Errorf("websocket protocol violation: Upgrade header %q does not contain websocket", r.Header.Get("Upgrade"))
+		err := fmt.Errorf("websocket protocol violation: Upgrade header %q does not contain websocket", r.Header.Get("Upgrade"))
 		http.Error(w, err.Error(), http.StatusBadRequest)
 		return err
 	}
 
 	if r.Method != "GET" {
-		err := xerrors.Errorf("websocket protocol violation: handshake request method is not GET but %q", r.Method)
+		err := fmt.Errorf("websocket protocol violation: handshake request method is not GET but %q", r.Method)
 		http.Error(w, err.Error(), http.StatusBadRequest)
 		return err
 	}
 
 	if r.Header.Get("Sec-WebSocket-Version") != "13" {
-		err := xerrors.Errorf("unsupported websocket protocol version (only 13 is supported): %q", r.Header.Get("Sec-WebSocket-Version"))
+		err := fmt.Errorf("unsupported websocket protocol version (only 13 is supported): %q", r.Header.Get("Sec-WebSocket-Version"))
 		http.Error(w, err.Error(), http.StatusBadRequest)
 		return err
 	}
 
 	if r.Header.Get("Sec-WebSocket-Key") == "" {
-		err := xerrors.New("websocket protocol violation: missing Sec-WebSocket-Key")
+		err := errors.New("websocket protocol violation: missing Sec-WebSocket-Key")
 		http.Error(w, err.Error(), http.StatusBadRequest)
 		return err
 	}
@@ -86,7 +86,7 @@ func verifyClientRequest(w http.ResponseWriter, r *http.Request) error {
 func Accept(w http.ResponseWriter, r *http.Request, opts *AcceptOptions) (*Conn, error) {
 	c, err := accept(w, r, opts)
 	if err != nil {
-		return nil, xerrors.Errorf("failed to accept websocket connection: %w", err)
+		return nil, fmt.Errorf("failed to accept websocket connection: %w", err)
 	}
 	return c, nil
 }
@@ -111,7 +111,7 @@ func accept(w http.ResponseWriter, r *http.Request, opts *AcceptOptions) (*Conn,
 
 	hj, ok := w.(http.Hijacker)
 	if !ok {
-		err = xerrors.New("passed ResponseWriter does not implement http.Hijacker")
+		err = errors.New("passed ResponseWriter does not implement http.Hijacker")
 		http.Error(w, http.StatusText(http.StatusNotImplemented), http.StatusNotImplemented)
 		return nil, err
 	}
@@ -130,7 +130,7 @@ func accept(w http.ResponseWriter, r *http.Request, opts *AcceptOptions) (*Conn,
 
 	netConn, brw, err := hj.Hijack()
 	if err != nil {
-		err = xerrors.Errorf("failed to hijack connection: %w", err)
+		err = fmt.Errorf("failed to hijack connection: %w", err)
 		http.Error(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
 		return nil, err
 	}
@@ -206,10 +206,10 @@ func authenticateOrigin(r *http.Request) error {
 	}
 	u, err := url.Parse(origin)
 	if err != nil {
-		return xerrors.Errorf("failed to parse Origin header %q: %w", origin, err)
+		return fmt.Errorf("failed to parse Origin header %q: %w", origin, err)
 	}
 	if strings.EqualFold(u.Host, r.Host) {
 		return nil
 	}
-	return xerrors.Errorf("request Origin %q is not authorized for Host %q", origin, r.Host)
+	return fmt.Errorf("request Origin %q is not authorized for Host %q", origin, r.Host)
 }

dial.go

@@ -5,15 +5,14 @@ import (
 	"bytes"
 	"context"
 	"encoding/base64"
+	"fmt"
 	"io"
 	"io/ioutil"
 	"math/rand"
 	"net/http"
 	"net/url"
 	"strings"
 	"sync"
-
-	"golang.org/x/xerrors"
 )
 
 // DialOptions represents the options available to pass to Dial.
@@ -44,7 +43,7 @@ type DialOptions struct {
 func Dial(ctx context.Context, u string, opts *DialOptions) (*Conn, *http.Response, error) {
 	c, r, err := dial(ctx, u, opts)
 	if err != nil {
-		return nil, r, xerrors.Errorf("failed to websocket dial: %w", err)
+		return nil, r, fmt.Errorf("failed to websocket dial: %w", err)
 	}
 	return c, r, nil
 }
@@ -62,15 +61,15 @@ func dial(ctx context.Context, u string, opts *DialOptions) (_ *Conn, _ *http.Re
 		opts.HTTPClient = http.DefaultClient
 	}
 	if opts.HTTPClient.Timeout > 0 {
-		return nil, nil, xerrors.Errorf("please use context for cancellation instead of http.Client.Timeout; see https://github.com/nhooyr/websocket/issues/67")
+		return nil, nil, fmt.Errorf("please use context for cancellation instead of http.Client.Timeout; see https://github.com/nhooyr/websocket/issues/67")
 	}
 	if opts.HTTPHeader == nil {
 		opts.HTTPHeader = http.Header{}
 	}
 
 	parsedURL, err := url.Parse(u)
 	if err != nil {
-		return nil, nil, xerrors.Errorf("failed to parse url: %w", err)
+		return nil, nil, fmt.Errorf("failed to parse url: %w", err)
 	}
 
 	switch parsedURL.Scheme {
@@ -79,7 +78,7 @@ func dial(ctx context.Context, u string, opts *DialOptions) (_ *Conn, _ *http.Re
 	case "wss":
 		parsedURL.Scheme = "https"
 	default:
-		return nil, nil, xerrors.Errorf("unexpected url scheme: %q", parsedURL.Scheme)
+		return nil, nil, fmt.Errorf("unexpected url scheme: %q", parsedURL.Scheme)
 	}
 
 	req, _ := http.NewRequest("GET", parsedURL.String(), nil)
@@ -95,7 +94,7 @@ func dial(ctx context.Context, u string, opts *DialOptions) (_ *Conn, _ *http.Re
 
 	resp, err := opts.HTTPClient.Do(req)
 	if err != nil {
-		return nil, nil, xerrors.Errorf("failed to send handshake request: %w", err)
+		return nil, nil, fmt.Errorf("failed to send handshake request: %w", err)
 	}
 	defer func() {
 		if err != nil {
@@ -114,7 +113,7 @@ func dial(ctx context.Context, u string, opts *DialOptions) (_ *Conn, _ *http.Re
 
 	rwc, ok := resp.Body.(io.ReadWriteCloser)
 	if !ok {
-		return nil, resp, xerrors.Errorf("response body is not a io.ReadWriteCloser: %T", rwc)
+		return nil, resp, fmt.Errorf("response body is not a io.ReadWriteCloser: %T", rwc)
 	}
 
 	c := &Conn{
@@ -132,19 +131,19 @@ func dial(ctx context.Context, u string, opts *DialOptions) (_ *Conn, _ *http.Re
 
 func verifyServerResponse(r *http.Request, resp *http.Response) error {
 	if resp.StatusCode != http.StatusSwitchingProtocols {
-		return xerrors.Errorf("expected handshake response status code %v but got %v", http.StatusSwitchingProtocols, resp.StatusCode)
+		return fmt.Errorf("expected handshake response status code %v but got %v", http.StatusSwitchingProtocols, resp.StatusCode)
 	}
 
 	if !headerValuesContainsToken(resp.Header, "Connection", "Upgrade") {
-		return xerrors.Errorf("websocket protocol violation: Connection header %q does not contain Upgrade", resp.Header.Get("Connection"))
+		return fmt.Errorf("websocket protocol violation: Connection header %q does not contain Upgrade", resp.Header.Get("Connection"))
 	}
 
 	if !headerValuesContainsToken(resp.Header, "Upgrade", "WebSocket") {
-		return xerrors.Errorf("websocket protocol violation: Upgrade header %q does not contain websocket", resp.Header.Get("Upgrade"))
+		return fmt.Errorf("websocket protocol violation: Upgrade header %q does not contain websocket", resp.Header.Get("Upgrade"))
 	}
 
 	if resp.Header.Get("Sec-WebSocket-Accept") != secWebSocketAccept(r.Header.Get("Sec-WebSocket-Key")) {
-		return xerrors.Errorf("websocket protocol violation: invalid Sec-WebSocket-Accept %q, key %q",
+		return fmt.Errorf("websocket protocol violation: invalid Sec-WebSocket-Accept %q, key %q",
 			resp.Header.Get("Sec-WebSocket-Accept"),
 			r.Header.Get("Sec-WebSocket-Key"),
 		)

example_echo_test.go

@@ -10,7 +10,6 @@ import (
 	"time"
 
 	"golang.org/x/time/rate"
-	"golang.org/x/xerrors"
 
 	"nhooyr.io/websocket"
 	"nhooyr.io/websocket/wsjson"
@@ -78,14 +77,14 @@ func echoServer(w http.ResponseWriter, r *http.Request) error {
 
 	if c.Subprotocol() != "echo" {
 		c.Close(websocket.StatusPolicyViolation, "client must speak the echo subprotocol")
-		return xerrors.Errorf("client does not speak echo sub protocol")
+		return fmt.Errorf("client does not speak echo sub protocol")
 	}
 
 	l := rate.NewLimiter(rate.Every(time.Millisecond*100), 10)
 	for {
 		err = echo(r.Context(), c, l)
 		if err != nil {
-			return xerrors.Errorf("failed to echo with %v: %w", r.RemoteAddr, err)
+			return fmt.Errorf("failed to echo with %v: %w", r.RemoteAddr, err)
 		}
 	}
 }
@@ -114,7 +113,7 @@ func echo(ctx context.Context, c *websocket.Conn, l *rate.Limiter) error {
 
 	_, err = io.Copy(w, r)
 	if err != nil {
-		return xerrors.Errorf("failed to io.Copy: %w", err)
+		return fmt.Errorf("failed to io.Copy: %w", err)
 	}
 
 	err = w.Close()

example_test.go

@@ -2,12 +2,11 @@ package websocket_test
 
 import (
 	"context"
+	"errors"
 	"log"
 	"net/http"
 	"time"
 
-	"golang.org/x/xerrors"
-
 	"nhooyr.io/websocket"
 	"nhooyr.io/websocket/wsjson"
 )
@@ -76,7 +75,7 @@ func ExampleCloseError() {
 
 	_, _, err = c.Reader(ctx)
 	var cerr websocket.CloseError
-	if !xerrors.As(err, &cerr) || cerr.Code != websocket.StatusNormalClosure {
+	if !errors.As(err, &cerr) || cerr.Code != websocket.StatusNormalClosure {
 		log.Fatalf("expected to be disconnected with StatusNormalClosure but got: %+v", err)
 		return
 	}

export_test.go

@@ -3,8 +3,7 @@ package websocket
 import (
 	"bufio"
 	"context"
-
-	"golang.org/x/xerrors"
+	"fmt"
 )
 
 type (
@@ -65,7 +64,7 @@ func (c *Conn) WriteHeader(ctx context.Context, h Header) error {
 	})
 	_, err := c.bw.Write(headerBytes)
 	if err != nil {
-		return xerrors.Errorf("failed to write header: %w", err)
+		return fmt.Errorf("failed to write header: %w", err)
 	}
 	if h.Fin {
 		err = c.Flush()

go.mod

@@ -1,6 +1,6 @@
 module nhooyr.io/websocket
 
-go 1.12
+go 1.13
 
 require (
 	github.com/fatih/color v1.7.0 // indirect
@@ -21,7 +21,6 @@ require (
 	golang.org/x/sys v0.0.0-20190830142957-1e83adbbebd0 // indirect
 	golang.org/x/time v0.0.0-20190308202827-9d24e82272b4
 	golang.org/x/tools v0.0.0-20190830223141-573d9926052a
-	golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7
 	gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127 // indirect
 	gotest.tools v2.2.0+incompatible // indirect
 	gotest.tools/gotestsum v0.3.6-0.20190825182939-fc6cb5870c52

header.go

@@ -5,8 +5,6 @@ import (
 	"fmt"
 	"io"
 	"math"
-
-	"golang.org/x/xerrors"
 )
 
 // First byte contains fin, rsv1, rsv2, rsv3.
@@ -145,7 +143,7 @@ func readHeader(b []byte, r io.Reader) (header, error) {
 	case payloadLength == 127:
 		h.payloadLength = int64(binary.BigEndian.Uint64(b))
 		if h.payloadLength < 0 {
-			return header{}, xerrors.Errorf("header with negative payload length: %v", h.payloadLength)
+			return header{}, fmt.Errorf("header with negative payload length: %v", h.payloadLength)
 		}
 		b = b[8:]
 	}

netconn.go

@@ -2,13 +2,12 @@ package websocket
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"io"
 	"math"
 	"net"
 	"time"
-
-	"golang.org/x/xerrors"
 )
 
 // NetConn converts a *websocket.Conn into a net.Conn.
@@ -97,7 +96,7 @@ func (c *netConn) Read(p []byte) (int, error) {
 		typ, r, err := c.c.Reader(c.readContext)
 		if err != nil {
 			var ce CloseError
-			if xerrors.As(err, &ce) && (ce.Code == StatusNormalClosure) || (ce.Code == StatusGoingAway) {
+			if errors.As(err, &ce) && (ce.Code == StatusNormalClosure) || (ce.Code == StatusGoingAway) {
 				c.eofed = true
 				return 0, io.EOF
 			}

statuscode.go

@@ -3,8 +3,6 @@ package websocket
 import (
 	"encoding/binary"
 	"fmt"
-
-	"golang.org/x/xerrors"
 )
 
 // StatusCode represents a WebSocket status code.
@@ -43,7 +41,8 @@ const (
 // CloseError represents a WebSocket close frame.
 // It is returned by Conn's methods when a WebSocket close frame is received from
 // the peer.
-// You will need to use https://godoc.org/golang.org/x/xerrors#As to check for this error.
+// You will need to use the https://golang.org/pkg/errors/#As function, new in Go 1.13,
+// to check for this error. See the CloseError example.
 type CloseError struct {
 	Code   StatusCode
 	Reason string
@@ -61,7 +60,7 @@ func parseClosePayload(p []byte) (CloseError, error) {
 	}
 
 	if len(p) < 2 {
-		return CloseError{}, xerrors.Errorf("close payload %q too small, cannot even contain the 2 byte status code", p)
+		return CloseError{}, fmt.Errorf("close payload %q too small, cannot even contain the 2 byte status code", p)
 	}
 
 	ce := CloseError{
@@ -70,7 +69,7 @@ func parseClosePayload(p []byte) (CloseError, error) {
 	}
 
 	if !validWireCloseCode(ce.Code) {
-		return CloseError{}, xerrors.Errorf("invalid status code %v", ce.Code)
+		return CloseError{}, fmt.Errorf("invalid status code %v", ce.Code)
 	}
 
 	return ce, nil
@@ -98,10 +97,10 @@ const maxControlFramePayload = 125
 
 func (ce CloseError) bytes() ([]byte, error) {
 	if len(ce.Reason) > maxControlFramePayload-2 {
-		return nil, xerrors.Errorf("reason string max is %v but got %q with length %v", maxControlFramePayload-2, ce.Reason, len(ce.Reason))
+		return nil, fmt.Errorf("reason string max is %v but got %q with length %v", maxControlFramePayload-2, ce.Reason, len(ce.Reason))
 	}
 	if !validWireCloseCode(ce.Code) {
-		return nil, xerrors.Errorf("status code %v cannot be set", ce.Code)
+		return nil, fmt.Errorf("status code %v cannot be set", ce.Code)
 	}
 
 	buf := make([]byte, 2+len(ce.Reason))