fix bug for stdin checksumming

hash.go

@@ -43,14 +43,18 @@ func hsh(files []string) chan result {
 	}
 
 	if len(files) == 0 {
+		r := make(chan result)
+		go func() {
 			hsh := h()
 			_, err := io.Copy(hsh, os.Stdin)
 			if err != nil {
 				fmt.Fprintf(os.Stderr, "%v\n", err)
 				os.Exit(1)
 			}
-		fmt.Printf("%x  -\n", hsh.Sum(nil))
-		return nil
+			r <- result{msg: fmt.Sprintf("%x  -", hsh.Sum(nil))}
+			close(r)
+		}()
+		return r
 	}
 
 	jobs := make(chan checksum)