JSON I/O

The jsonio package exposes a value as an io.Reader (JsonReader) or an io.Writer (JsonWriter) by marshaling/unmarshaling it over an io.Pipe. This is useful when an API wants to speak in terms of io.Reader/io.Writer but the payload is a typed Go value.

Reading through a JsonReader

NewReader(v) wraps io.Pipe() and encodes v into the pipe in the background. The returned *JsonReader is an io.Reader that yields the JSON encoding of v:

r := jsonio.NewReader(order)
resp, err := http.Post("https://example.com/orders", "application/json", r)

An encoding failure is delivered as a read error, so the consumer observes it at io.ReadAll or upload time rather than at construction.

Writing through a JsonWriter

NewWriter(v) returns an io.Writer. Anything written to it is JSON-decoded into the destination v when the writer is closed; decodes happen incrementally as bytes arrive:

var got userCreateRequest
w := jsonio.NewWriter(&got)

resp := httptest.NewRequest("POST", "/users", w)

w.Close()       // flush and finish decoding into got

This keeps handlers that accept streaming uploads usable for JSON requests without buffering the whole body in memory yourself.