Add *Conn. CopyFromTextual, CopyToTextual, which use textual format for copying data

copy_done.go

@@ -0,0 +1,30 @@
+package pgproto3
+
+import (
+	"encoding/json"
+)
+
+type CopyDone struct {
+}
+
+func (*CopyDone) Backend() {}
+
+func (dst *CopyDone) Decode(src []byte) error {
+	if len(src) != 0 {
+		return &invalidMessageLenErr{messageType: "CopyDone", expectedLen: 0, actualLen: len(src)}
+	}
+
+	return nil
+}
+
+func (src *CopyDone) Encode(dst []byte) []byte {
+	return append(dst, 'c', 0, 0, 0, 4)
+}
+
+func (src *CopyDone) MarshalJSON() ([]byte, error) {
+	return json.Marshal(struct {
+		Type string
+	}{
+		Type: "CopyDone",
+	})
+}

frontend.go

@@ -22,6 +22,7 @@ type Frontend struct {
 	copyData             CopyData
 	copyInResponse       CopyInResponse
 	copyOutResponse      CopyOutResponse
+	copyDone             CopyDone
 	dataRow              DataRow
 	emptyQueryResponse   EmptyQueryResponse
 	errorResponse        ErrorResponse
@@ -72,6 +73,8 @@ func (b *Frontend) Receive() (BackendMessage, error) {
 		msg = &b.closeComplete
 	case 'A':
 		msg = &b.notificationResponse
+	case 'c':
+		msg = &b.copyDone
 	case 'C':
 		msg = &b.commandComplete
 	case 'd':