build: drop support for go1.9

cmd/serve/restic/stdio_conn.go

@@ -1,10 +1,9 @@
-// +build go1.9
-
 package restic
 
 import (
 	"net"
 	"os"
+	"time"
 )
 
 // Addr implements net.Addr for stdin/stdout.
@@ -52,3 +51,23 @@ func (s *StdioConn) LocalAddr() net.Addr {
 func (s *StdioConn) RemoteAddr() net.Addr {
 	return Addr{}
 }
+
+// SetDeadline sets the read/write deadline.
+func (s *StdioConn) SetDeadline(t time.Time) error {
+	err1 := s.stdin.SetReadDeadline(t)
+	err2 := s.stdout.SetWriteDeadline(t)
+	if err1 != nil {
+		return err1
+	}
+	return err2
+}
+
+// SetReadDeadline sets the read/write deadline.
+func (s *StdioConn) SetReadDeadline(t time.Time) error {
+	return s.stdin.SetReadDeadline(t)
+}
+
+// SetWriteDeadline sets the read/write deadline.
+func (s *StdioConn) SetWriteDeadline(t time.Time) error {
+	return s.stdout.SetWriteDeadline(t)
+}