Stop json.Marshal() from stripping trailing zero from floating point number

Question

I got the following problem: My golang program converts some information into JSON. For example it results in the following json:

{
   \"value\":40,
   \"uni         


        

Answer 1

I had a similar issue where I wanted to marshal a map[string]interface{} with float values f.x 1.0 to JSON as 1.0. I solved it by adding a custom Marshal function for a custom float type and then replace the floats in the map with the custom type:

type customFloat float64

func (f customFloat) MarshalJSON() ([]byte, error) {
    if float64(f) == math.Trunc(float64(f)) {
        return []byte(fmt.Sprintf("%.1f", f)), nil
    }
    return json.Marshal(float64(f))
}

func replaceFloat(value map[string]interface{}) {
    for k, v := range value {
        switch val := v.(type) {
        case map[string]interface{}:
            replaceFloat(val)
        case float64:
            value[k] = customFloat(val)
        }
    }
}

Then replace all float64 nodes:

replaceFloat(myValue)
bytes, err := json.Marshal(myValue)

This will print the floats like 1.0