Importing packages in Go - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of importing and using fmt package

What is the output of this Go program?

Go

package main

import "fmt"

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

A Hello, Go!

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

C Hello Go

D Compilation error

💡 Hint

Look at what fmt.Println prints to the screen.

The fmt package's Println function prints the string with a newline. So the output is exactly "Hello, Go!".

❓ Predict Output

intermediate

Output when importing multiple packages

What is the output of this Go program?

Go

package main

import (
    "fmt"
    "math"
)

func main() {
    fmt.Println(int(math.Sqrt(16)))
}

A Compilation error

B 16

C 4

D 0

💡 Hint

math.Sqrt returns a float64. Casting to int truncates decimals.

math.Sqrt(16) returns 4.0 as float64. Casting to int converts it to 4. So fmt.Println prints 4.

❓ Predict Output

advanced

Output when importing a package with alias

What is the output of this Go program?

Go

package main

import f "fmt"

func main() {
    f.Println("Alias import works!")
}

A Compilation error: alias import not allowed

B f.Println("Alias import works!")

C Compilation error: undefined f

D Alias import works!

💡 Hint

The alias f replaces fmt in this program.

The import alias f allows calling fmt functions using f. So f.Println prints the string correctly.

❓ Predict Output

advanced

Output when importing a package but not using it

What happens when you run this Go program?

Go

package main

import "fmt"

func main() {
    // fmt package is imported but not used
}

A Compilation error: imported and not used: "fmt"

B Program runs with no output

C Runtime error

D Warning but runs successfully

💡 Hint

Go does not allow unused imports.

Go compiler requires all imported packages to be used. Since fmt is imported but not used, it causes a compilation error.

🧠 Conceptual

expert

Understanding blank identifier import

What is the effect of importing a package using the blank identifier (_) in Go?

A It imports the package and renames all its exported functions to start with _.

B It imports the package solely for its side effects without making its exported names available.

C It causes a compilation error because _ is not a valid alias.

D It imports the package and allows using its exported names with the _ prefix.

💡 Hint

Think about why you would import a package but never call its functions directly.

Using _ as the import alias imports the package only for its initialization side effects, like running init functions, without exposing its exported names.