Importing packages in Go - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of importing packages in Go?

Importing packages allows you to use code written in other files or libraries, so you don't have to write everything from scratch.

beginner

How do you import a single package in Go?

Use the <code>import</code> keyword followed by the package name in quotes, like <code>import "fmt"</code>.

beginner

How do you import multiple packages in Go?

Use parentheses to group imports, like:<br><pre>import (
  "fmt"
  "math"
)</pre>

intermediate

What happens if you import a package but don't use it in Go?

Go will give a compile error because it requires all imported packages to be used. This helps keep code clean.

intermediate

How can you rename an imported package in Go?

You can give a package a new name by writing it before the package path, like <code>import io "io/ioutil"</code>. Then use <code>io</code> to refer to it.

Which keyword is used to import packages in Go?

A import

B include

C using

D require

The import keyword is used to bring packages into your Go program.

How do you import multiple packages at once?

A import ( "fmt" "math" )

B import "fmt", "math"

C import ("fmt" "math")

D import fmt math

Multiple packages are imported using parentheses with each package on its own line or separated by newlines.

What error occurs if you import a package but don't use it?

A Warning only

B No error, it's allowed

C Runtime error

D Compile error

Go requires all imported packages to be used, otherwise it gives a compile error.

How do you rename an imported package?

A import rename "package/path"

B import newname "package/path"

C import "package/path" newname

D import "package/path" as newname

You write the new name before the package path in the import statement.

Which of these is a valid import statement?

A import fmt

B import (fmt)

C import "fmt"

D import fmt "fmt"

Package names must be in quotes when imported.

Explain how to import single and multiple packages in Go with examples.

Think about how you bring in one package versus many packages.

What happens if you import a package but do not use it in your Go program? Why does Go enforce this?

Consider Go's strictness about unused code.

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