feat: embed greyproxy.yml as default config when no -C flag is passed

Uses Go's //go:embed to bake greyproxy.yml into the binary so it
works out of the box without requiring an external config file.

Author: tito

cmd/greyproxy/program.go

@@ -10,6 +10,7 @@ import (
 	"strings"
 	"syscall"
 
+	defaults "github.com/greyhavenhq/greyproxy"
 	"github.com/greyhavenhq/greyproxy/internal/gostcore/logger"
 	"github.com/greyhavenhq/greyproxy/internal/gostcore/service"
 	greyproxy "github.com/greyhavenhq/greyproxy/internal/greyproxy"
@@ -37,12 +38,13 @@ type program struct {
 
 func (p *program) Init(env svc.Environment) error {
 	parser.Init(parser.Args{
-		CfgFile:     cfgFile,
-		Services:    services,
-		Nodes:       nodes,
-		Debug:       debug,
-		Trace:       trace,
-		MetricsAddr: metricsAddr,
+		CfgFile:       cfgFile,
+		DefaultConfig: defaults.DefaultConfig,
+		Services:      services,
+		Nodes:         nodes,
+		Debug:         debug,
+		Trace:         trace,
+		MetricsAddr:   metricsAddr,
 	})
 
 	return nil

defaultconfig.go

@@ -0,0 +1,9 @@
+package greyproxy
+
+import _ "embed"
+
+// DefaultConfig is the embedded default greyproxy.yml configuration.
+// It is used when no -C flag is provided on the command line.
+//
+//go:embed greyproxy.yml
+var DefaultConfig []byte

internal/gostx/config/parsing/parser/parser.go

@@ -2,6 +2,7 @@ package parser
 
 import (
 	"bufio"
+	"bytes"
 	"encoding/json"
 	"os"
 	"strings"
@@ -28,12 +29,13 @@ func Parse() (*config.Config, error) {
 }
 
 type Args struct {
-	CfgFile     string
-	Services    []string
-	Nodes       []string
-	Debug       bool
-	Trace       bool
-	MetricsAddr string
+	CfgFile       string
+	DefaultConfig []byte // embedded default config (used when CfgFile is empty)
+	Services      []string
+	Nodes         []string
+	Debug         bool
+	Trace         bool
+	MetricsAddr   string
 }
 
 type parser struct {
@@ -68,6 +70,11 @@ func (p *parser) Parse() (*config.Config, error) {
 				return nil, err
 			}
 		}
+	} else if len(p.args.DefaultConfig) > 0 {
+		// No -C flag: use the embedded default configuration.
+		if err := cfg.Read(bytes.NewReader(p.args.DefaultConfig), "yaml"); err != nil {
+			return nil, err
+		}
 	}
 
 	cmdCfg, err := cmd.BuildConfigFromCmd(p.args.Services, p.args.Nodes)