Crowdly

Copying a mutex closes it

Mutex is an interface and interfaces cannot be copied

Mutex values can exist only on the heap

It makes the resulting slice read-only

What is the primary effect of the third index in the full slice expression below?

s2 := s[2:4:4]

It limits the capacity of the resulting slice

It copies the elements into a new backing array

It fixes the length and prevents reslicing

What happens if close is called on an already closed channel?

The channel is reopened

Nothing

A runtime panic occurs

close returns false

What is printed by the following Go code?

func f() {
    x := 1
    defer fmt.Println(x)
    x = 2
}
f()

Synchronization exists only for channels of pointer values

For an unbuffered channel, which statement best describes a successful send and its corresponding receive?

They synchronize the communicating goroutines at that communication

Only the sender is synchronized

They provide no synchronization relationship

What is printed by the following Go code?

s1 := []int{1, 2, 3, 4}
s2 := s1[:2]
s2 = append(s2, 10)
fmt.Println(s1)

Any receiver should close the channel as soon as it has enough data

Which guideline most directly reduces the risk of sending on a closed channel?

The sending side that owns completion should normally be responsible for closing the channel

Every consumer should defer close(ch)

Channels should be closed after every receive

To release associated resources and propagate cancellation to descendants

Why should code normally call the cancel function returned by context.WithCancel, context.WithTimeout, or context.WithDeadline when it is done with the context?

To make Context safe for concurrent use

To convert the context into context.Background

To reset the parent context's deadline

func Load(id int) and create context.Background inside it

Which API design follows the usual Go convention for a function that needs a context?

Store context.Context in a global variable instead of passing it

func Load(id int, ctx context.Context)

func Load(ctx context.Context, id int)

What is printed by the following Go code?

s1 := make([]int, 2, 2)
s1[0], s1[1] = 1, 2
s2 := append(s1, 3)
s2[0] = 10
fmt.Println(s1)