time.RFC3339

[jc-fireball]

Hi

We've been migrating to huma. We notice the default time format is using RFC3339nano in json response. Is there anyway we can set the time format in json to time.RFC3339

[danielgtaylor]

@jc-fireball sorry for the slow response on this! The Go JSON marshaler controls this behavior via the time.Time type's MarshalJSON method. See https://pkg.go.dev/time#Time.MarshalJSON and the official implementation at https://cs.opensource.google/go/go/+/refs/tags/go1.23.2:src/time/time.go;l=1392.

You should be able to create a custom type wrapping time.Time that implements custom marshaling as explained at https://stackoverflow.com/questions/23695479/how-to-format-timestamp-in-outgoing-json. If you can't use custom types then you may have to wrap the JSON marshaler itself in the huma.Config formats to special case certain behaviors.

[jc-fireball]

As you just point out, the Golang default time.Time marshal is using RFC3339, however Huma default to RFC3339Nano

[jc-fireball]

Only the time.Time in header is in different way which allows us to override the format but not in other places like json field.

[danielgtaylor]

@jc-fireball that specific code you linked to is Huma's custom handling of parameters (path/query/header/cookie). You can change that time format like this using Go's time formatting:

type MyInput struct {
  MyTime time.Time `query:"myTime" timeFormat:"..."`
}

Keep in mind though this is not for the JSON body, which is controlled by the encoding/json package instead of Huma itself which I linked to above. This is just how Go works with JSON encoding, but you can preprocess times to get the output you want, for example:

t := time.Now()
t = t.Add(123 * time.Millisecond)
b, _ := json.Marshal(t)
fmt.Println(string(b)) // prints with milliseconds

t = t.Truncate(time.Second)
b, _ = json.Marshal(t)
fmt.Println(string(b)) // prints without milliseconds

https://go.dev/play/p/ayaM260jpFQ