Importing packages in Go - Mini Project: Build & Apply

Importing packages

📖 Scenario: You are writing a simple Go program that uses a package to print text to the screen.

🎯 Goal: Learn how to import a package and use a function from it to display a message.

📋 What You'll Learn

Create a Go file with a main package

Import the fmt package

Use fmt.Println to print a message

💡 Why This Matters

🌍 Real World

Importing packages is how Go programs use code written by others or in other files, like printing text or doing math.

💼 Career

Knowing how to import and use packages is essential for writing real Go programs in software development jobs.

1

Create the main package and function

Write the first two lines to create a Go program with package main and a func main() function.

Go

package main

func main() {
    // Your code here
}

Hint

Every Go program starts with a package declaration and a main function to run.

2

Import the fmt package

Add an import statement to import the fmt package right after package main.

Go

package main

import "fmt"

func main() {
    // Your code here
}

Hint

Use import "fmt" to bring in the package for printing.

3

Use fmt.Println to print a message

Inside the main function, write fmt.Println("Hello, Go!") to print the message.

Go

package main

import "fmt"

func main() {
    // Your code here
}

Hint

Use fmt.Println to print text with a new line.

4

Run the program to see the output

Write fmt.Println("Hello, Go!") is already done. Now run the program and print the output.

Go

package main

import "fmt"

func main() {
    fmt.Println("Hello, Go!")
    // Your code here
}

Hint

Running the program should print Hello, Go! to the screen.

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