How to cast < -chan amqp.Delivery to < -chan interface{}?

Question

go

For an example sketched such code. The purpose of the function is to return a channel with an interface to implement the channel's abstract type.

package main

import (
  "fmt"
  "github.com/streadway/amqp"
)

type (
  IConsumer interface {
    Consume() (<-chan interface{}, error)
  }
  AmqpConsumer struct {
    conn    *amqp.Connection
    topic   string
    channel *amqp.Channel
  }
)

func (pr *AmqpConsumer) Consume() (<-chan interface{}, error) {
  var msgs <-chan interface{}

  ch, err := pr.conn.Channel()
  if err != nil {
    return msgs, err
  }
  defer ch.Close()

  amqp_msgs, err := ch.Consume(
    pr.topic, // queue
    "",       // consumer
    true,     // auto-ack
    false,    // exclusive
    false,    // no-local
    false,    // no-wait
    nil,      // args
  )
  if err != nil {
    return msgs, err
  }

  return amqp_msgs, nil
}

func main() {
  fmt.Println("Hello, playground")
}

https://play.golang.org/p/VTRDQjYOclf

Getting error

./prog.go:41:2: cannot use amqp_msgs (type <-chan amqp.Delivery) as type <-chan interface {} in return argument

Answer 1

Casting channels seems to be impossible in go. You will have to create an intermediate channel. That's pretty much how I see it. But most likely it does not work as it should
https://play.golang.org/p/i8-69C6RDrG

package main

import (
  "fmt"
  "github.com/streadway/amqp"
)

type (
  IConsumer interface {
    Consume() (<-chan interface{}, error)
  }
  AmqpConsumer struct {
    conn    *amqp.Connection
    topic   string
    channel *amqp.Channel
  }
)

func (pr *AmqpConsumer) Consume() (<-chan interface{}, error) {
  var msgs <-chan interface{}

  ch, err := pr.conn.Channel()
  if err != nil {
    return msgs, err
  }
  defer ch.Close()

  amqp_msgs, err := ch.Consume(
    pr.topic, // queue
    "",       // consumer
    true,     // auto-ack
    false,    // exclusive
    false,    // no-local
    false,    // no-wait
    nil,      // args
  )
  if err != nil {
    return msgs, err
  }

  var castCh chan interface{}
  go func() {
    for msg := range amqp_msgs {
      castCh <- msg
    }
  }()
  
  return castCh, nil
}

func main() {
  fmt.Println("Hello, playground")
}