Infinite loops in Go - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an infinite loop in Go?

An infinite loop is a loop that never stops running because its exit condition is never met or it has no exit condition.

beginner

How do you write a simple infinite loop in Go?

You can write an infinite loop using for {} without any condition inside the braces.

beginner

Why should you be careful with infinite loops?

Because they can cause your program to freeze or use too much CPU if not controlled or stopped properly.

intermediate

How can you stop an infinite loop in Go?

You can use a break statement inside the loop when a certain condition is met to exit the loop.

beginner

What is the output of this Go code?

for {
  fmt.Println("Hello")
  break
}

The output is:

Hello

The loop prints "Hello" once and then stops because of the break.

Which of the following is a correct infinite loop in Go?

A for {}

B for i := 0; i < 10; i++ {}

C while true {}

D loop {}

In Go, for {} creates an infinite loop. There is no while or loop keyword.

What keyword can you use to exit an infinite loop in Go?

A break

B exit

C stop

D return

The break keyword stops the nearest enclosing loop immediately.

What happens if an infinite loop has no break or exit condition?

A The program stops automatically

B The loop runs once

C The program crashes immediately

D The loop runs forever, possibly freezing the program

Without a way to stop, the loop runs forever, which can freeze or slow down the program.

Which of these is NOT a reason to use an infinite loop?

A Running a server that listens for requests

B Calculating a fixed sum once

C Waiting for user input continuously

D Polling a sensor repeatedly

Calculating a fixed sum once does not need an infinite loop; infinite loops are for repeated or continuous tasks.

How can you safely use an infinite loop in Go?

A Never use infinite loops

B Use <code>for i := 0; i < 10; i++ {}</code>

C Use <code>for {}</code> with a <code>break</code> inside based on a condition

D Use <code>while true {}</code>

Using for {} with a break lets you control when to stop the loop safely.

Explain what an infinite loop is and how to create one in Go.

Think about a loop that never ends unless you tell it to stop.

Describe how to safely stop an infinite loop in Go and why it is important.

Consider what happens if a loop never stops and how to prevent that.

Practice

1. What does the following Go code do?

for { }

easy

A. Runs an infinite loop that never stops

B. Runs a loop 10 times

C. Runs a loop only once

D. Causes a syntax error

Solution

1. Step 1: Understand the loop syntax

   The code uses for { } which is Go's way to write an infinite loop without conditions.

2. Step 2: Analyze loop behavior

   Since there is no break or condition, the loop runs forever without stopping.

3. Final Answer:

   Runs an infinite loop that never stops -> Option A

4. Quick Check:

   for { } means infinite loop [OK]

Hint: for { } always means infinite loop in Go [OK]

Common Mistakes:

• Thinking it runs a fixed number of times
• Assuming it causes a syntax error
• Confusing with loops that have conditions

2. Which of the following is the correct syntax for an infinite loop in Go?

easy

A. for i := 0; i < 10; i++ { }

B. loop forever { }

C. for { }

D. while true { }

Solution

1. Step 1: Review Go loop syntax

   Go does not have a while or loop keyword; infinite loops use for { }.

2. Step 2: Identify correct infinite loop

   for { } uses for { }, which is the correct infinite loop syntax in Go.

3. Final Answer:

   for { } -> Option C

4. Quick Check:

   Go infinite loop syntax = for { } [OK]

Hint: Remember: Go uses for { } for infinite loops [OK]

Common Mistakes:

• Using while or loop keywords (not in Go)
• Confusing for loops with conditions as infinite
• Syntax errors from invalid keywords

3. What will be the output of this Go program?

package main
import "fmt"
func main() {
  count := 0
  for {
    if count == 3 {
      break
    }
    fmt.Println(count)
    count++
  }
}

medium

A. 0 1 2

B. 0 1 2 3

C. Infinite printing of numbers

D. No output

Solution

1. Step 1: Understand loop and break condition

   The loop runs infinitely but breaks when count equals 3.

2. Step 2: Trace output values

   It prints count values 0, 1, 2 then breaks before printing 3.

3. Final Answer:

   0 1 2 -> Option A

4. Quick Check:

   Loop breaks at count==3, prints 0 to 2 [OK]

Hint: Break stops infinite loop at condition [OK]

Common Mistakes:

• Expecting 3 to be printed
• Thinking loop runs forever
• Ignoring break statement

4. Identify the problem in this Go code that causes an infinite loop and fix it:

package main
import "fmt"
func main() {
  i := 0
  for i < 5 {
    fmt.Println(i)
  }
}

medium

A. Add break statement without increment

B. Change for to for { }

C. Remove the loop entirely

D. Add i++ inside the loop to increment i

Solution

1. Step 1: Identify loop condition and variable

   The loop runs while i < 5 but i is never changed inside the loop.

2. Step 2: Fix infinite loop by incrementing i

   Adding i++ inside the loop updates i, allowing the loop to end.

3. Final Answer:

   Add i++ inside the loop to increment i -> Option D

4. Quick Check:

   Increment loop variable to avoid infinite loop [OK]

Hint: Always update loop variable to prevent infinite loops [OK]

Common Mistakes:

• Forgetting to increment loop variable
• Adding break without changing i causes infinite loop
• Changing loop to infinite loop syntax accidentally

5. How can you safely implement an infinite loop in Go that stops after 5 seconds?

hard

A. Use for i := 0; i < 5; i++ { }

B. Use for { } with time.After and break when 5 seconds pass

C. Use while true with a timer

D. Use for { } without any break or condition

Solution

1. Step 1: Understand infinite loop with timeout

   Use for { } for infinite loop and time.After to wait 5 seconds.

2. Step 2: Break loop after 5 seconds

   Inside loop, check if 5 seconds passed and use break to stop loop safely.

3. Final Answer:

   Use for { } with time.After and break when 5 seconds pass -> Option B

4. Quick Check:

   Infinite loop + timer + break = safe stop [OK]

Hint: Combine for { } with timer and break to stop [OK]

Common Mistakes:

• Using invalid while syntax
• Not breaking loop causes infinite run
• Using fixed count loop instead of infinite