Add experimental Fetch API package

fetch/fetch/fetch.go

@@ -0,0 +1,66 @@
+package fetch
+
+import (
+	"io"
+	"net/http"
+	"net/url"
+	"runtime/js"
+)
+
+type Method int
+
+func (m Method) String() string {
+	switch m {
+	case GET:
+		return "GET"
+	case POST:
+		return "POST"
+	case PUT:
+		return "PUT"
+	case DELETE:
+		return "DELETE"
+	case PATCH:
+		return "PATCH"
+	}
+
+	panic("unsupported method")
+}
+
+const (
+	GET Method = iota
+	POST
+	PUT
+	DELETE
+	PATCH
+)
+
+type Request struct {
+	Method  Method
+	URL     *url.URL
+	Headers http.Header
+	Body    []byte
+}
+
+type Response struct {
+	URL        url.URL
+	Headers    http.Header
+	Body       io.Reader
+	StatusCode int
+}
+
+func Fetch(req Request) (Response, error) {
+	init := js.Global.Get("Object").New()
+	init.Set("method", req.Method.String())
+	init.Set("body", req.Body)
+
+	headers := js.Global.Get("Headers").New()
+	for header, values := range req.Headers {
+		for _, value := range values {
+			headers.Call("append", header, value)
+		}
+	}
+	init.Set("headers", headers)
+
+	promise := js.Global.Call("fetch", req.URL.String(), init)
+	return Response{}, nil
+}