convert co/yield to to async/await

yield-to-async.js

// https://astexplorer.net/#/gist/48d24982fceb3f258cc2dcd764fe8e38/937f48fc25443224a08bb20774a7d8868052770c

export default function ({types: t}) {
  return {
    visitor: {
      ObjectMethod(path) {
        if (path.node.generator) {
          path.node.async = true        
          path.node.generator = false        
        }
	  },
      ClassMethod(path) {
        if (path.node.generator) {
          path.node.async = true        
          path.node.generator = false        
        }
	  },
      FunctionExpression(path) {
        if (path.node.generator) {
          path.node.async = true        
          path.node.generator = false        
        }
      },
      FunctionDeclaration(path) {
        if (path.node.generator) {
          path.node.async = true        
          path.node.generator = false        
        }
	  },
      YieldExpression: function(path) {
    	let argument = path.node.argument
    	path.replaceWith(t.awaitExpression(argument), false)
      }
    }
  }
}