Crowdly

The channel is initialized automatically

It panics

It immediately returns 0

Deferred functions in the panicking goroutine run, then the program terminates

What is the effect of an unrecovered panic in a goroutine?

The panic is automatically converted to an error returned to main

The goroutine is restarted by the runtime

Only that goroutine silently terminates and the program continues normally

RWMutex makes ordinary map access safe without using its locking methods

Which statement about sync.RWMutex is correct?

Multiple readers may hold read locks concurrently when no writer holds the lock

Multiple writers may hold the write lock concurrently

A read lock automatically upgrades to a write lock

Using one atomic operation automatically makes a multi-variable invariant atomic

Which statement about atomic operations is correct?

Atomic operations can participate in synchronization, but related accesses still require a coherent synchronization design

Every atomic operation must be surrounded by a mutex

Atomic operations work only on stack variables

%v wraps the error, while %w converts it to a string

What is the important difference between %w and %v when an error is passed to fmt.Errorf?

%w works only when the error is nil

%w creates wrapping that can be inspected through the error chain, while %v only formats the value

There is no behavioral difference

Which command runs tests with Go's race detector enabled?

The receive always panics

What happens when receiving from a closed channel after all buffered values have been received?

The channel is reopened

The zero value is returned immediately

The receive blocks forever

The existing backing array is always extended in place

What can happen when append exceeds the capacity of a slice?

A new backing array may be allocated

The program always panics

The oldest element is removed

They automatically create database indexes

Why are parameterized SQL queries preferred over building queries by concatenating untrusted input?

They eliminate the need for database transactions

They always execute faster

They help prevent SQL injection by separating query structure from parameter values

What is printed by the following Go code?

m := map[string]int{"a": 1}
v, ok := m["b"]
fmt.Print(v, ok)