What about filepath.FromSlash("./"+cmd)?

Ooh, missed that one. Still feels a little hacky, but it's better than the others!

Another option, which I just now noticed, is to create the *exec.Cmd without the the use of exec.Command(), since the purpose of that function is to resolve the path.

&exec.Cmd{Path: cmd}

From https://golang.org/pkg/os/exec/#Cmd:

    // Path is the path of the command to run.
    //
    // This is the only field that must be set to a non-zero
    // value. If Path is relative, it is evaluated relative
    // to Dir.
    Path string

   ...

    // Dir specifies the working directory of the command.
    // If Dir is the empty string, Run runs the command in the
    // calling process's current directory.
    Dir string

Edit: exec.Command() properly sets Cmd.Args to []string{cmd, arg1, arg2, ...} as well, so there is one extra step if you have arguments to pass.

Personally, I don't feel like we need a helper function in os/exec that depends on os.Getwd

I've only needed to do this a few times and I just used a full path with a directory like os.Getwd. That's at most a few extra lines, and in my opinion it's self-explanatory and simple.

I feel like adding extra API or magic to os/exec to avoid a bit of typing is unnecessary.

This seems like a non-problem. People can write "./foo", which works everywhere already, or they can use a full path with os.Getwd, as @mvdan suggests. If this really happens a lot, then instead of

"." + string(filepath.Separator) + cmd

define

const dotSlash = "." + string(filepath.Separator)

and write dotSlash + cmd.