Fetch API for Go

📥 The WHATWG Fetch API for Go

type Todo struct {
  UserID int
  ID int
  Title string
  Completed bool
}
response, err := fetch.Fetch("https://jsonplaceholder.typicode.com/todos/1")
if err != nil {
  log.Fatal(err)
}
var todo Todo
err = response.JSONInto(&todo)
if err != nil {
  log.Fatal(err)
}
log.Println("todo=%#+v", todo)
// Output: ...

Installation

You can install this package using go get right from your command line:

go get github.com/jcbhmr/go-fetch

Or if you prefer you can import it in your Go code and use go mod tidy to automagically ✨ add it to your go.mod.

import "github.com/jcbhmr/go-fetch"

Usage

package main

import (
  "log"

  "github.com/jcbhmr/go-fetch"
)

func main() {
  response, err := fetch.Fetch("https://example.com/")
  if err != nil {
    log.Fatal(err)
  }
  text, err := response.Text()
  if err != nil {
    log.Fatal(err)
  }
  log.Println("%s returned this %s:", response.URL(), response.Headers().Get("Content-Type"))
  log.Println(text)
}

Development

WebIDL's primary language integration is between C++ and JavaScript but a lot of the constructs remain relatively portable. In this case, though, we are implementing & consuming the Fetch API using Go! That means there's some things to be aware of about how the WebIDL-defined API is translated into somewhat idiomatic Go code.

1. Names are transformed into Go-conformant PascalCase names to be properly exported.
2. optional parameters become nil-able *T types if the original type is un-nil-able (like string, int, etc.). If the original type is nil-able then it stays as-is (like a *MyStruct parameter).
3. Sum types that can't be shoehorned in using sealed interface hacks (like MyStruct|string since you can't do interfaces on primitives) are defined as any and annotated with a developer note.
4. DOMString and USVString are both represented using the Go string primitive. They are mostly considered interchangable. This might be changed later. 🤷‍♂️
5. ByteString is also just a Go string.
6. JavaScript-native Promise<T> has been replaced with a <-chan Result[T]
7. BufferSource where possible is a []byte|[]uint8|[]int8|[]uint16|... union
8. ArrayBuffer is considered to be equivalent to []byte
9. Go versions of WebIDL enums rely on the user to know the possible enum values. So type RequestCredentials = string.
10. All WebIDL-defined properties are exposed through getter and setter methods. There is no prefix for getters and a Set prefix for setters. For instance myStruct.Value() and myStruct.SetValue() would be the getter/setter for MyStruct#value.
11. This package does expose non-[Exposed=...] WebIDL types that are not available to JavaScript.
12. WebIDL dictionary structs always have all their fields made nil-able similar to optional parameters unless they are marked required.
13. iterable<K,V> means that it has an .Iter() method that returns a Seq2[K,V] function which can be used with https://go.dev/wiki/RangefuncExperiment
14. iterable<V> means that it has an .Iter() method that returns a Seq[V] function which can be used with https://go.dev/wiki/RangefuncExperiment
15. In places where a TypeError would be thrown it will panic()
16. In places where a DOMException would be thrown it will return an error
17. sequence<T> is taken to be equivalent to []T