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.

Practice

1. What is the correct way to import a single package named fmt in Go?

easy

A. include fmt

B. import "fmt"

C. using fmt

D. require "fmt"

Solution

1. Step 1: Understand Go import syntax

   In Go, packages are imported using the keyword import followed by the package name in double quotes.

2. Step 2: Check each option

   Only import "fmt" uses the correct syntax: import "fmt". Other options use incorrect keywords or missing quotes.

3. Final Answer:

   import "fmt" -> Option B

4. Quick Check:

   Go import single package = import "package" [OK]

Hint: Use import with quotes around package name [OK]

Common Mistakes:

• Forgetting quotes around package name
• Using wrong keywords like include or require
• Missing import keyword

2. Which of the following is the correct syntax to import multiple packages fmt and math in Go?

easy

A. import (
"fmt"
"math"
)

B. import ("fmt", "math")

C. import "fmt" "math"

D. import fmt, math

Solution

1. Step 1: Recall multi-package import syntax

   In Go, multiple packages are imported inside parentheses with each package name in quotes on separate lines.

2. Step 2: Analyze options

   import ( "fmt" "math" ) correctly uses parentheses and places each package name on its own line with quotes. Options B, C, and D are incorrect syntax.

3. Final Answer:

   import ( "fmt" "math" ) -> Option A

4. Quick Check:

   Multiple imports use parentheses and quotes [OK]

Hint: Use parentheses and quotes for multiple imports [OK]

Common Mistakes:

• Missing parentheses for multiple imports
• Not putting package names in quotes
• Separating packages with commas instead of new lines

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

package main
import (
  "fmt"
  "math"
)
func main() {
  fmt.Println(math.Sqrt(16))
}

medium

A. Error: undefined math.Sqrt

B. 4

C. 16

D. 4.0

Solution

1. Step 1: Understand the code

   The program imports fmt and math packages. It calls math.Sqrt(16) which returns the square root of 16 as a float64.

2. Step 2: Determine output type

   math.Sqrt(16) returns 4.0 (float64). fmt.Println prints it as 4.0 including the decimal point because it is a float64 value.

3. Final Answer:

   4.0 -> Option D

4. Quick Check:

   math.Sqrt(16) = 4.0 [OK]

Hint: math.Sqrt returns float64, prints as 4.0 including decimal [OK]

Common Mistakes:

• Expecting integer output instead of float64
• Thinking math package is not imported
• Confusing output with error

4. Identify the error in this Go code snippet:

package main
import "fmt"
import "math"
func main() {
  fmt.Println(math.Pow(2, 3))
}

medium

A. Cannot import multiple packages separately

B. Missing parentheses for multiple imports

C. No error, code runs fine

D. math.Pow does not exist

Solution

1. Step 1: Check import statements

   Go allows multiple import statements separately or grouped in parentheses. Both are valid.

2. Step 2: Verify function usage

   math.Pow(2, 3) is a valid function call to calculate 2 to the power 3.

3. Final Answer:

   No error, code runs fine -> Option C

4. Quick Check:

   Separate imports allowed = no error [OK]

Hint: Multiple import statements are allowed separately [OK]

Common Mistakes:

• Thinking multiple imports must be in parentheses
• Assuming math.Pow does not exist
• Confusing import syntax rules

5. You want to import the strings package but use it with the name str in your code. Which import statement is correct?

hard

A. import str "strings"

B. import "str" as "strings"

C. import strings as str

D. import str from "strings"

Solution

1. Step 1: Understand alias import syntax in Go

   To use a package with a different name, Go allows aliasing by writing the alias before the package name in quotes.

2. Step 2: Check options

   import str "strings" uses correct syntax: import str "strings". Other options use invalid syntax not supported in Go.

3. Final Answer:

   import str "strings" -> Option A

4. Quick Check:

   Alias import = alias before package in quotes [OK]

Hint: Alias package by writing alias before quoted package name [OK]

Common Mistakes:

• Using 'as' keyword which Go does not support
• Trying to import with 'from' keyword
• Placing alias after package name