Always buffer all publish framed together

Even if the user doesn't await basicPublish all framed beloging to one
publish should be published together. So intead of waiting for a
potentially blocked socket to be drain enqueue all data and only await
for the last sent frame.

Fixes #49

src/amqp-channel.ts

@@ -338,12 +338,13 @@ export class AMQPChannel {
     buffer.setUint8(j, 206); j += 1 // frame end byte
     buffer.setUint32(headerStart + 3, j - headerStart - 8) // update frameSize
 
+    let lastFrame
     // Send current frames if there's no body to send
     if (body.byteLength === 0) {
-      await this.connection.send(new Uint8Array(buffer.buffer, 0, j))
+      lastFrame = this.connection.send(new Uint8Array(buffer.buffer, 0, j))
     } else if (j >= buffer.byteLength - 8) {
       // Send current frames if a body frame can't fit in the rest of the frame buffer
-      await this.connection.send(new Uint8Array(buffer.buffer, 0, j))
+      lastFrame = this.connection.send(new Uint8Array(buffer.buffer, 0, j))
       j = 0
     }
 
@@ -358,10 +359,11 @@ export class AMQPChannel {
       const bodyView = new Uint8Array(buffer.buffer, j, frameSize)
       bodyView.set(dataSlice); j += frameSize // body content
       buffer.setUint8(j, 206); j += 1 // frame end byte
-      await this.connection.send(new Uint8Array(buffer.buffer, 0, j))
+      lastFrame = this.connection.send(new Uint8Array(buffer.buffer, 0, j))
       bodyPos += frameSize
       j = 0
     }
+    await lastFrame // buffer all frames and only wait for the last as RabbitMQ requires all publish frames to be sent together
     this.connection.bufferPool.push(buffer) // return buffer to buffer pool for later reuse
     // if publish confirm is enabled, put a promise on a queue if the sends were ok
     // the promise on the queue will be fullfilled by the read loop when an ack/nack