Writing first Go program - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple Go program

What is the output of this Go program?

Go

package main
import "fmt"
func main() {
    fmt.Println("Hello, Go!")
}

A Hello Go!

B hello, go!

C hello Go

D Hello, Go!

💡 Hint

Look carefully at the exact string inside fmt.Println.

The program prints exactly what is inside the quotes, including capitalization and punctuation.

🧠 Conceptual

intermediate

Purpose of the main function in Go

What is the role of the main function in a Go program?

A It imports packages needed by the program.

B It defines global variables for the program.

C It is the starting point where the program begins execution.

D It handles errors during program execution.

💡 Hint

Think about where the computer starts running your code.

In Go, the main function is where the program starts running. Without it, the program has no entry point.

🔧 Debug

advanced

Identify the error in this Go program

What error will this Go program produce when run?

Go

package main
import "fmt"
func main() {
    fmt.Println("Welcome to Go")
    fmt.Println("Let's learn")
    fmt.Println("Go is fun")
}

A Runtime error: index out of range

B Syntax error: missing closing parenthesis

C Compilation error: undefined function

D No error, program runs fine

💡 Hint

Check the parentheses in the last fmt.Println line.

The last fmt.Println call is missing a closing parenthesis, causing a syntax error.

📝 Syntax

advanced

Correct way to import and use fmt package

Which option shows the correct way to import the fmt package and print "Go Rocks"?

A

import "fmt"
func main() { fmt.Println("Go Rocks") }

B

import fmt
func main() { fmt.Println("Go Rocks") }

C

import (fmt)
func main() { fmt.Println("Go Rocks") }

D

import fmt;
func main() { fmt.Println("Go Rocks") }

💡 Hint

Remember how Go imports packages with quotes.

Go imports packages using import "packageName" syntax. Parentheses are used for multiple imports.

🚀 Application

expert

Output of a Go program with variable and fmt.Printf

What is the output of this Go program?

Go

package main
import "fmt"
func main() {
    name := "Go Learner"
    age := 3
    fmt.Printf("%s is %d years old.\n", name, age)
}

A Go Learner is 3 years old.

B Go Learner 3 years old.

C %s is %d years old.

D Go Learner is years old 3.

💡 Hint

Look at how fmt.Printf formats strings with %s and %d.

fmt.Printf replaces %s with the string variable and %d with the integer variable in order.

Practice

1. What is the purpose of the main function in a Go program?

easy

A. It is the starting point where the program begins execution.

B. It defines a package for the program.

C. It imports external libraries.

D. It declares variables for the program.

Solution

1. Step 1: Understand the role of main function

   The main function is special in Go; it is where the program starts running.

2. Step 2: Differentiate from other parts

   Packages define code grouping, imports bring libraries, and variables store data, but none start execution.

3. Final Answer:

   It is the starting point where the program begins execution. -> Option A

4. Quick Check:

   Program starts at main() -> D [OK]

Hint: Remember: main() is the program's entry point [OK]

Common Mistakes:

• Confusing package declaration with program start
• Thinking imports start the program
• Assuming variables control program flow

2. Which of the following is the correct way to print "Hello, Go!" in a Go program?

easy

A. fmt.Println("Hello, Go!")

B. print("Hello, Go!")

C. fmt.print("Hello, Go!")

D. console.log("Hello, Go!")

Solution

1. Step 1: Identify the correct print function in Go

   Go uses the fmt package with Println to print with a newline.

2. Step 2: Check syntax correctness

   fmt.Println("Hello, Go!") is correct; others are either wrong function names or from other languages.

3. Final Answer:

   fmt.Println("Hello, Go!") -> Option A

4. Quick Check:

   Use fmt.Println() to print lines in Go [OK]

Hint: Use fmt.Println() for printing with newline [OK]

Common Mistakes:

• Using fmt.print instead of fmt.Println
• Using print() which is not standard in Go
• Using console.log from JavaScript

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

package main
import "fmt"
func main() {
    fmt.Println("Welcome to Go!")
}

medium

A. package main
import "fmt"
func main() {
fmt.Println("Welcome to Go!")
}

B. fmt.Println("Welcome to Go!")

C. Welcome to Go!

D. Error: missing main function

Solution

1. Step 1: Understand program structure

   The program imports fmt and defines main(), which prints the string.

2. Step 2: Identify output of fmt.Println

   It prints the string exactly: Welcome to Go! with a newline.

3. Final Answer:

   Welcome to Go! -> Option C

4. Quick Check:

   fmt.Println prints string output [OK]

Hint: fmt.Println prints the string content, not code [OK]

Common Mistakes:

• Confusing code with output
• Expecting code to print itself
• Thinking main function is missing

4. Identify the error in this Go program:

package main
import "fmt"
func main() {
    fmt.Println("Hello, world!"
}

medium

A. Missing import statement

B. Incorrect function name

C. Missing package declaration

D. Missing closing parenthesis in fmt.Println call

Solution

1. Step 1: Check syntax of fmt.Println

   The call to fmt.Println is missing a closing parenthesis at the end.

2. Step 2: Verify other parts

   Package and import are present, function name is correct, so no errors there.

3. Final Answer:

   Missing closing parenthesis in fmt.Println call -> Option D

4. Quick Check:

   Check parentheses in function calls [OK]

Hint: Count opening and closing parentheses carefully [OK]

Common Mistakes:

• Forgetting closing parenthesis in function calls
• Assuming missing import or package causes this error
• Misnaming main function

5. You want to write a Go program that prints "Hello" on one line and "World" on the next line. Which code snippet achieves this correctly?

hard

A. package main
import "fmt"
func main() {
fmt.Print("Hello\nWorld")
}

B. package main
import "fmt"
func main() {
fmt.Println("Hello")
fmt.Println("World")
}

C. package main
import "fmt"
func main() {
fmt.Println("Hello\nWorld")
}

D. package main
import "fmt"
func main() {
fmt.Print("Hello")
fmt.Print("World")
}

Solution

1. Step 1: Understand printing with new lines

   fmt.Println prints text and adds a newline automatically.

2. Step 2: Check each option's output

   A: Two fmt.Println calls print "Hello" on one line and "World" on the next. Correct.
   B: fmt.Print("Hello\nWorld") prints "Hello\nWorld" (with actual newline) on one line.
   C: fmt.Println("Hello\nWorld") prints "Hello\nWorld" (with actual newline) followed by newline, so output is two lines.
   D: Two fmt.Print calls print "HelloWorld" on one line.

3. Final Answer:

   package main import "fmt" func main() { fmt.Println("Hello") fmt.Println("World") } -> Option B

4. Quick Check:

   Use fmt.Println twice for separate lines [OK]

Hint: Use fmt.Println for each line to print separately [OK]

Common Mistakes:

• Using fmt.Print without newline causes joined output
• Expecting \n inside fmt.Println to create new line
• Confusing fmt.Print and fmt.Println behavior