On macOS Sierra 10.12, fkill --force by process name throws exception because pkill does not support -9 flag

[sompylasar]

$ fkill --force node
AggregateError: 
    Error: Killing process node failed: pkill: illegal option -- 9
    usage: pkill [-signal] [-ILfilnovx] [-F pidfile] [-G gid]
                 [-P ppid] [-U uid] [-g pgrp]
                 [-t tty] [-u euid] pattern ...
        at Array.map (<anonymous>)
        at processExists.all.then.then (/Users/ivanbabak/.nvm/versions/node/v8.7.0/lib/node_modules/fkill-cli/node_modules/fkill/index.js:83:10)
        at <anonymous>
    at processExists.all.then.then (/Users/ivanbabak/.nvm/versions/node/v8.7.0/lib/node_modules/fkill-cli/node_modules/fkill/index.js:83:10)
    at <anonymous>
    at process._tickCallback (internal/process/next_tick.js:188:7)

fkill/index.js

Lines 16 to 23 in 23503ec

	function macOSKill(input, opts) {
	const killByName = typeof input === 'string';
	const cmd = killByName ? 'pkill' : 'kill';
	const args = [input];
	if (opts.force) {
	args.unshift('-9');
	}

[sindresorhus]

Not interested in supporting macOS 10.12.