fix: user errors.As for error type assertion

Author: aeneasr

crdb/error.go

@@ -16,23 +16,6 @@ package crdb
 
 import "fmt"
 
-// errorCause returns the original cause of the error, if possible. An
-// error has a proximate cause if it's type is compatible with Go's
-// errors.Unwrap() or pkg/errors' Cause(); the original cause is the
-// end of the causal chain.
-func errorCause(err error) error {
-	for err != nil {
-		if c, ok := err.(interface{ Cause() error }); ok {
-			err = c.Cause()
-		} else if c, ok := err.(interface{ Unwrap() error }); ok {
-			err = c.Unwrap()
-		} else {
-			break
-		}
-	}
-	return err
-}
-
 type txError struct {
 	cause error
 }

crdb/tx.go

@@ -19,6 +19,7 @@ package crdb
 import (
 	"context"
 	"database/sql"
+	"errors"
 
 	"github.com/lib/pq"
 )
@@ -193,16 +194,17 @@ func errIsRetryable(err error) bool {
 }
 
 func errCode(err error) string {
-	switch t := errorCause(err).(type) {
-	case *pq.Error:
-		return string(t.Code)
-
-	case errWithSQLState:
-		return t.SQLState()
+	var pqe *pq.Error
+	if errors.As(err, &pqe) {
+		return string(pqe.Code)
+	}
 
-	default:
-		return ""
+	var sqlErr errWithSQLState
+	if errors.As(err, &sqlErr) {
+		return sqlErr.SQLState()
 	}
+
+	return ""
 }
 
 // errWithSQLState is implemented by pgx (pgconn.PgError).