Add 'Channel.all'.

lib/index.js

@@ -364,6 +364,26 @@ const Channel = function(length = 0) {
   );
 };
 
+Channel.all = channels => {
+  const output = Channel();
+
+  (async () => {
+    for (;;) {
+      const values = await Promise.all(channels.map(Channel.shift));
+
+      if (values.every(value => value === undefined)) {
+        break;
+      } else {
+        await output.push(values);
+      }
+    }
+
+    await output.close();
+  })();
+
+  return output;
+};
+
 // Node.js stream.readable
 const fromNodeStream = (channel, stream) => {
   stream.on(`readable`, async () => {