Function buildHandlerAsPackageMain

packages/go/src/index.ts:552–595

* Builds the wrapped Go function using the legacy mode where package name is * `"main"` and we need `main.go` in the same dir as the entrypoint, otherwise * `go build` will refuse to build.

({
  entrypointAbsolute,
  entrypointDirname,
  go,
  handlerFunctionName,
  outDir,
  undo,
}: BuildHandlerOptions)

 * `go build` will refuse to build.
 */
async function buildHandlerAsPackageMain({
  entrypointAbsolute,
  entrypointDirname,
  go,
  handlerFunctionName,
  outDir,
  undo,
}: BuildHandlerOptions): Promise<void> {
  debug('Building Go handler as package "main" (legacy)');

  await writeEntrypoint(
    join(entrypointDirname, MAIN_GO_FILENAME),
    '',
    handlerFunctionName
  );

  undo.fileActions.push({
    to: undefined, // delete
    from: join(entrypointDirname, MAIN_GO_FILENAME),
  });

  // `go get` will look at `*.go` (note we set `cwd`), parse the `import`s
  // and download any packages that aren't part of the stdlib
  debug('Running `go get`...');
  try {
    await go.get();
  } catch (err) {
    console.error('Failed to `go get`');
    throw err;
  }

  debug('Running `go build`...');
  const destPath = join(outDir, HANDLER_FILENAME);
  try {
    const src = [
      join(entrypointDirname, MAIN_GO_FILENAME),
      entrypointAbsolute,
    ].map(file => normalize(file));
    await go.build(src, destPath);
  } catch (err) {
    console.error('failed to `go build`');
    throw err;
  }
}

async function renameHandlerFunction(fsPath: string, from: string, to: string) {
  let fileContents = await readFile(fsPath, 'utf8');