Import fixes from pgx/pgproto3

Import and adapt commit: fbb8cce

backend.go

@@ -14,7 +14,6 @@ type Backend struct {
 	// Frontend message flyweights
 	bind            Bind
 	_close          Close
-	copyFail        CopyFail
 	describe        Describe
 	execute         Execute
 	flush           Flush
@@ -81,8 +80,6 @@ func (b *Backend) Receive() (FrontendMessage, error) {
 		msg = &b.describe
 	case 'E':
 		msg = &b.execute
-	case 'f':
-		msg = &b.copyFail
 	case 'H':
 		msg = &b.flush
 	case 'P':

copy_fail.go

@@ -8,11 +8,10 @@ import (
 )
 
 type CopyFail struct {
-	Error string
+	Message string
 }
 
-func (*CopyFail) Frontend() {}
-func (*CopyFail) Backend()  {}
+func (*CopyFail) Backend() {}
 
 func (dst *CopyFail) Decode(src []byte) error {
 	idx := bytes.IndexByte(src, 0)
@@ -20,17 +19,17 @@ func (dst *CopyFail) Decode(src []byte) error {
 		return &invalidMessageFormatErr{messageType: "CopyFail"}
 	}
 
-	dst.Error = string(src[:idx])
+	dst.Message = string(src[:idx])
 
 	return nil
 }
 
 func (src *CopyFail) Encode(dst []byte) []byte {
-	dst = append(dst, 'C')
+	dst = append(dst, 'f')
 	sp := len(dst)
 	dst = pgio.AppendInt32(dst, -1)
 
-	dst = append(dst, src.Error...)
+	dst = append(dst, src.Message...)
 	dst = append(dst, 0)
 
 	pgio.SetInt32(dst[sp:], int32(len(dst[sp:])))
@@ -40,10 +39,10 @@ func (src *CopyFail) Encode(dst []byte) []byte {
 
 func (src *CopyFail) MarshalJSON() ([]byte, error) {
 	return json.Marshal(struct {
-		Type  string
-		Error string
+		Type    string
+		Message string
 	}{
-		Type:  "CopyFail",
-		Error: src.Error,
+		Type:    "CopyFail",
+		Message: src.Message,
 	})
 }

copy_out_response.go

@@ -44,6 +44,8 @@ func (src *CopyOutResponse) Encode(dst []byte) []byte {
 	sp := len(dst)
 	dst = pgio.AppendInt32(dst, -1)
 
+	dst = append(dst, src.OverallFormat)
+
 	dst = pgio.AppendUint16(dst, uint16(len(src.ColumnFormatCodes)))
 	for _, fc := range src.ColumnFormatCodes {
 		dst = pgio.AppendUint16(dst, fc)