td, err := os.Open("testdata/src/pkg")
	if err != nil {
		t.Fatal(err)
	}
	fis, err := td.Readdir(0)
	if err != nil {
		t.Fatal(err)
	}
	for _, fi := range fis {
		if !fi.IsDir() {
			continue
		}

		// TODO(gri) remove extra pkg directory eventually
		goldenFile := filepath.Join("testdata", "src", "pkg", fi.Name(), "golden.txt")
		w := NewWalker(nil, "testdata/src/pkg")
		pkg, _ := w.import_(fi.Name())

	echo "$targ already exists; remove before continuing"
	exit 2
fi

unset GOROOT
src=$(cd .. && pwd)
echo "#### Copying to $targ"
cp -Rp "$src" "$targ"
cd "$targ"
echo
echo "#### Cleaning $targ"
chmod -R +w .
rm -f .gitignore
if [ -e .git ]; then
	git clean -f -d
fi
echo
echo "#### Building $targ"
echo
cd src
./make.bash --no-banner $forceflag
gohostos="$(../bin/go env GOHOSTOS)"

					},

					// func copyBytesToGo(dst []byte, src ref) (int, bool)
					"syscall/js.copyBytesToGo": (sp) => {
						sp >>>= 0;
						const dst = loadSlice(sp + 8);
						const src = loadValue(sp + 32);
						if (!(src instanceof Uint8Array || src instanceof Uint8ClampedArray)) {
							this.mem.setUint8(sp + 48, 0);
							return;
						}
						const toCopy = src.subarray(0, dst.length);
						dst.set(toCopy);

"%GOTOOLDIR%/dist"...

	// Optimal case is where the underlying reader implements io.WriterTo
	srcBuf := bytes.NewBuffer(make([]byte, 8192))
	src := NewReader(srcBuf)
	dstBuf := new(bytes.Buffer)
	dst := onlyWriter{dstBuf}
	for i := 0; i < b.N; i++ {
		srcBuf.Reset()
		src.Reset(srcBuf)
		dstBuf.Reset()
		io.Copy(dst, src)
	}
}

func BenchmarkReaderCopyUnoptimal(b *testing.B) {

package main

import (
	"fmt"
	"go/ast"
	"go/format"
	"go/parser"
	"go/scanner"
	"go/token"
	"os"
	"strings"
)

func parse(name string, src []byte, flags parser.Mode) *ast.File {
	ast1, err := parser.ParseFile(fset, name, src, flags)
	if err != nil {
		if list, ok := err.(scanner.ErrorList); ok {
			// If err is a scanner.ErrorList, its String will print just
			// the first error and then (+n more errors).

file. This allows pre-compiled static libraries to be included in the package
directory and linked properly.
For example if package foo is in the directory /go/src/foo:

	// #cgo LDFLAGS: -L${SRCDIR}/libs -lfoo

Will be expanded to:

	// #cgo LDFLAGS: -L/go/src/foo/libs -lfoo

When the Go tool sees that one or more Go files use the special import
"C", it will look for other non-Go files in the directory and compile

	for i := 2; ; i++ {
		ch <- i  // Send 'i' to channel 'ch'.
	}
}

// Copy the values from channel 'src' to channel 'dst',
// removing those divisible by 'prime'.
func filter(src <-chan int, dst chan<- int, prime int) {
	for i := range src {  // Loop over values received from 'src'.
		if i%prime != 0 {
			dst <- i  // Send 'i' to channel 'dst'.
		}
	}
}

Vendoring in std and cmd
========================

The Go command maintains copies of external packages needed by the
standard library in the src/vendor and src/cmd/vendor directories.

There are two modules, std and cmd, defined in src/go.mod and
src/cmd/go.mod. When a package outside std or cmd is imported
by a package inside std or cmd, the import path is interpreted
as if it had a "vendor/" prefix. For example, within "crypto/tls",

	"unicode"

	"cmd/asm/internal/flags"
	"cmd/internal/objabi"
	"cmd/internal/src"
)

// A Tokenizer is a simple wrapping of text/scanner.Scanner, configured
// for our purposes and made a TokenReader. It forms the lowest level,
// turning text from readers into tokens.
type Tokenizer struct {
	tok  ScanToken
	s    *scanner.Scanner
	base *src.PosBase
	line int
	file *os.File // If non-nil, file descriptor to close.
}