print readable variables with golang

Question

How to print a map, struct or whatever in a readable way?

With PHP you can to this

echo \'
\';
print_r($var);
echo \'
\';
         


        

Answer 1

For debugging I use this:

func printVars(w io.Writer, writePre bool, vars ...interface{}) {
    if writePre {
        io.WriteString(w, "
\n")
    }
    for i, v := range vars {
        fmt.Fprintf(w, "» item %d type %T:\n", i, v)
        j, err := json.MarshalIndent(v, "", "    ")
        switch {
        case err != nil:
            fmt.Fprintf(w, "error: %v", err)
        case len(j) < 3: // {}, empty struct maybe or empty string, usually mean unexported struct fields
            w.Write([]byte(html.EscapeString(fmt.Sprintf("%+v", v))))
        default:
            w.Write(j)
        }
        w.Write([]byte("\n\n"))
    }
    if writePre {
        io.WriteString(w, "
\n")
    }
}

playground