Switching to yarn

src/index.ts

@@ -3,7 +3,7 @@ import {ensureYarnIsInstalled} from './yarn'
 import {run} from './run'
 import {resolve} from 'path'
 
-const main = async () => {
+const main = async (): Promise<void> => {
   await ensureYarnIsInstalled()
 
   const cmd: string = getInput('cmd', {required: true})

src/run.ts

@@ -1,5 +1,5 @@
 import {exec} from '@actions/exec'
 
-export const run = async (cmd: string, {cwd}: {cwd: string}) => {
+export const run = async (cmd: string, {cwd}: {cwd: string}): Promise<void> => {
   await exec('yarn', cmd.split(' '), {cwd})
 }

src/yarn.ts

@@ -2,7 +2,7 @@ import {debug, setOutput} from '@actions/core'
 import {exec, getExecOutput} from '@actions/exec'
 import {which} from '@actions/io'
 
-export const ensureYarnIsInstalled = async () => {
+export const ensureYarnIsInstalled = async (): Promise<void> => {
   try {
     await which('yarn', true)
   } catch (e) {