Why select is needed in Go - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to wait on multiple channels using select.

Go

select {
case msg := <-ch1:
    fmt.Println("Received", msg)
case [1]:
    fmt.Println("Timeout")
}

Drag options to blanks, or click blank then click option'

A<-time.After(time.Second)

Bmsg := <-ch2

C<-done

D<-ch1

Attempts:

3 left

💡 Hint

Common Mistakes

Using a receive from the wrong channel without timeout.

Not including a timeout case causing blocking.

The select statement waits on multiple channel operations. Using case <-time.After(time.Second) adds a timeout case.

2fill in blank

medium

Complete the select statement to handle messages from two channels.

Go

select {
case msg1 := <-ch1:
    fmt.Println("From ch1:", msg1)
case [1]:
    fmt.Println("From ch2:", msg2)
}

Drag options to blanks, or click blank then click option'

Amsg2 := <-ch2

Bmsg2 := <-ch1

Cmsg1 := <-ch2

Dmsg1 := <-done

Attempts:

3 left

💡 Hint

Common Mistakes

Receiving from the same channel twice.

Using wrong variable names causing confusion.

The select waits on both ch1 and ch2. The second case must receive from ch2.

3fill in blank

hard

Fix the error in the select statement to avoid blocking.

Go

select {
case msg := <-ch1:
    fmt.Println(msg)
[1]:
    fmt.Println("No message received")
}

Drag options to blanks, or click blank then click option'

Acase msg := <-ch2

Bcase <-time.After(time.Second)

Ccase <-done

Ddefault

Attempts:

3 left

💡 Hint

Common Mistakes

Using a timeout channel instead of default when immediate fallback is needed.

Omitting default causing the program to block.

The default case in select runs if no other case is ready, preventing blocking.

4fill in blank

hard

Fill both blanks to create a select that handles two channels and a default case.

Go

select {
case msg := <-ch1:
    fmt.Println("ch1:", msg)
case [1]:
    fmt.Println("ch2:", msg)
default:
    fmt.Println([2])
}

Drag options to blanks, or click blank then click option'

Amsg := <-ch2

B"No messages"

Cmsg := <-done

D"Waiting..."

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong channel names in cases.

Putting a channel receive in default case.

The select listens on ch1 and ch2. The default prints a message when no channels are ready.

5fill in blank

hard

Fill all three blanks to create a select that handles two channels and a timeout.

Go

select {
case msg := <-[1]:
    fmt.Println("Received from first channel:", msg)
case msg := <-[2]:
    fmt.Println("Received from second channel:", msg)
case <-[3]:
    fmt.Println("Timeout occurred")
}

Drag options to blanks, or click blank then click option'

Ach1

Bch2

Ctime.After(time.Second)

Ddone

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up channel names.

Using a variable instead of time.After for timeout.

The select waits on ch1, ch2, and a timeout channel from time.After.