Add experimental gRPC-Web folder

vendor/github.com/johanbrandhorst/fetch/.gitignore

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+.vscode

vendor/github.com/johanbrandhorst/fetch/README.md

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+# Fetch
+The Go http.Transport interface implemented over the WHATWG Fetch API using the WebAssembly arch target.
+
+## Usage
+
+This package requires the Go WASM compilation target to be supported.
+See [my wasm-experiments repo](github.com/johanbrandhorst/wasm-experiments)
+for and example of its use.

vendor/github.com/johanbrandhorst/fetch/fetch.go

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+// +build js,wasm
+
+package fetch
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"strconv"
+	"syscall/js"
+)
+
+// Adapted for syscall/js from
+// https://github.com/gopherjs/gopherjs/blob/8dffc02ea1cb8398bb73f30424697c60fcf8d4c5/compiler/natives/src/net/http/fetch.go
+
+// streamReader implements an io.ReadCloser wrapper for ReadableStream of https://fetch.spec.whatwg.org/.
+type streamReader struct {
+	pending []byte
+	stream  js.Value
+}
+
+func (r *streamReader) Read(p []byte) (n int, err error) {
+	if len(r.pending) == 0 {
+		var (
+			bCh   = make(chan []byte)
+			errCh = make(chan error)
+		)
+		r.stream.Call("read").Call("then",
+			js.NewCallback(func(args []js.Value) {
+				result := args[0]
+				if result.Get("done").Bool() {
+					errCh <- io.EOF
+					return
+				}
+				value := make([]byte, result.Get("value").Get("byteLength").Int())
+				js.ValueOf(value).Call("set", result.Get("value"))
+				bCh <- value
+			}),
+			js.NewCallback(func(args []js.Value) {
+				// Assumes it's a DOMException.
+				errCh <- errors.New(args[0].Get("message").String())
+			}),
+		)
+		select {
+		case b := <-bCh:
+			r.pending = b
+		case err := <-errCh:
+			return 0, err
+		}
+	}
+	n = copy(p, r.pending)
+	r.pending = r.pending[n:]
+	return n, nil
+}
+
+func (r *streamReader) Close() error {
+	// This ignores any error returned from cancel method. So far, I did not encounter any concrete
+	// situation where reporting the error is meaningful. Most users ignore error from resp.Body.Close().
+	// If there's a need to report error here, it can be implemented and tested when that need comes up.
+	r.stream.Call("cancel")
+	return nil
+}
+
+// Transport is a RoundTripper that is implemented using the WHATWG Fetch API.
+// It supports streaming response bodies.
+type Transport struct{}
+
+// RoundTrip performs a full round trip of a request.
+func (t *Transport) RoundTrip(req *http.Request) (*http.Response, error) {
+	headers := js.Global.Get("Headers").New()
+	for key, values := range req.Header {
+		for _, value := range values {
+			headers.Call("append", key, value)
+		}
+	}
+
+	ac := js.Global.Get("AbortController").New()
+
+	opt := js.Global.Get("Object").New()
+	opt.Set("headers", headers)
+	opt.Set("method", req.Method)
+	opt.Set("credentials", "same-origin")
+	opt.Set("signal", ac.Get("signal"))
+
+	if req.Body != nil {
+		body, err := ioutil.ReadAll(req.Body)
+		if err != nil {
+			_ = req.Body.Close() // RoundTrip must always close the body, including on errors.
+			return nil, err
+		}
+		_ = req.Body.Close()
+		opt.Set("body", body)
+	}
+	respPromise := js.Global.Call("fetch", req.URL.String(), opt)
+	if respPromise == js.Undefined {
+		return nil, errors.New("your browser does not support the Fetch API, please upgrade")
+	}
+
+	var (
+		respCh = make(chan *http.Response)
+		errCh  = make(chan error)
+	)
+	respPromise.Call("then",
+		js.NewCallback(func(args []js.Value) {
+			result := args[0]
+			header := http.Header{}
+			result.Get("headers").Call("forEach", js.NewCallback(func(args []js.Value) {
+				key, value := args[0].String(), args[1].String()
+				ck := http.CanonicalHeaderKey(key)
+				header[ck] = append(header[ck], value)
+			}))
+
+			contentLength := int64(-1)
+			if cl, err := strconv.ParseInt(header.Get("Content-Length"), 10, 64); err == nil {
+				contentLength = cl
+			}
+
+			b := result.Get("body")
+			if b == js.Undefined {
+				errCh <- errors.New("your browser does not support the ReadableStream API, please upgrade")
+				return
+			}
+
+			select {
+			case respCh <- &http.Response{
+				Status:        result.Get("status").String() + " " + http.StatusText(result.Get("status").Int()),
+				StatusCode:    result.Get("status").Int(),
+				Header:        header,
+				ContentLength: contentLength,
+				Body:          &streamReader{stream: b.Call("getReader")},
+				Request:       req,
+			}:
+			case <-req.Context().Done():
+			}
+		}),
+		js.NewCallback(func(args []js.Value) {
+			select {
+			case errCh <- fmt.Errorf("net/http: fetch() failed: %s", args[0].String()):
+			case <-req.Context().Done():
+			}
+		}),
+	)
+	select {
+	case <-req.Context().Done():
+		// Abort the Fetch request
+		ac.Call("abort")
+		return nil, errors.New("net/http: request canceled")
+	case resp := <-respCh:
+		return resp, nil
+	case err := <-errCh:
+		return nil, err
+	}
+}