Practical use cases in Go - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a common use case for Go in web development?

Go is often used to build fast and efficient web servers and APIs due to its strong support for concurrency and simple syntax.

beginner

How does Go handle concurrent tasks in practical applications?

Go uses goroutines, which are lightweight threads managed by the Go runtime, allowing easy and efficient concurrent execution.

beginner

Why is Go popular for building command-line tools?

Go compiles to a single binary with no dependencies, making it easy to distribute and run command-line tools across different systems.

intermediate

What makes Go suitable for cloud services and microservices?

Go's fast startup time, efficient memory use, and built-in support for networking make it ideal for scalable cloud services and microservices.

intermediate

How can Go be used in data processing tasks?

Go's concurrency features allow it to process large data sets efficiently by running multiple tasks in parallel, speeding up data processing.

Which Go feature allows running multiple tasks at the same time?

A Interfaces

B Pointers

C Structs

D Goroutines

Goroutines are lightweight threads in Go that enable concurrent execution.

Why is Go a good choice for building command-line tools?

A It requires a virtual machine to run

B It compiles to a single binary with no external dependencies

C It uses dynamic typing

D It has a large standard GUI library

Go compiles programs into a single executable file that can run independently.

What makes Go suitable for cloud microservices?

A Slow compilation

B Heavy runtime dependencies

C Fast startup and efficient memory use

D Lack of networking support

Go's fast startup and efficient memory use help build scalable cloud microservices.

In Go, what is the main benefit of using goroutines for data processing?

A They allow parallel processing to speed up tasks

B They increase program size

C They slow down execution

D They prevent concurrency

Goroutines enable running multiple tasks at once, making data processing faster.

Which of these is NOT a typical practical use case for Go?

A Writing mobile apps with native UI

B Building web servers

C Creating command-line tools

D Developing cloud microservices

Go is not commonly used for native mobile UI apps; other languages are preferred for that.

Describe three practical use cases where Go is a strong choice and explain why.

Think about Go's speed, concurrency, and compilation features.

Explain how Go's concurrency model benefits real-world applications.

Focus on how goroutines make running many tasks easier and faster.

Practice

1. Which Go feature is commonly used to create a simple web server that listens on a port?

easy

A. The net/http package with http.ListenAndServe

B. The fmt package with Println

C. The os package with Open

D. The math package with Pow

Solution

1. Step 1: Identify the package for web servers

   The net/http package provides tools to create web servers in Go.

2. Step 2: Recognize the function to start the server

   http.ListenAndServe starts a server listening on a specified port.

3. Final Answer:

   The net/http package with http.ListenAndServe -> Option A

4. Quick Check:

   Web server = net/http.ListenAndServe [OK]

Hint: Web servers use net/http.ListenAndServe to listen on ports [OK]

Common Mistakes:

• Confusing printing functions with server functions
• Using file operations instead of network functions
• Thinking math package handles networking

2. Which of the following is the correct syntax to open a file named "data.txt" for reading in Go?

easy

A. file, err := os.Open("data.txt")

B. file := os.OpenFile("data.txt", os.O_WRONLY)

C. file, err := ioutil.ReadFile("data.txt")

D. file := os.Read("data.txt")

Solution

1. Step 1: Identify the function to open a file for reading

   os.Open opens a file in read-only mode and returns a file and error.

2. Step 2: Check the syntax correctness

   The syntax file, err := os.Open("data.txt") correctly assigns both file and error.

3. Final Answer:

   file, err := os.Open("data.txt") -> Option A

4. Quick Check:

   Open file for reading = os.Open [OK]

Hint: Use os.Open with two variables to open files safely [OK]

Common Mistakes:

• Using os.Read which does not exist
• Using ioutil.ReadFile which reads whole file, not opens
• Opening file with wrong flags for reading

3. What will be the output of this Go code snippet?

package main
import "fmt"
func main() {
    nums := []int{2, 4, 6}
    squares := make(map[int]int)
    for _, n := range nums {
        squares[n] = n * n
    }
    fmt.Println(squares)
}

medium

A. map[2:4 4:8 6:12]

B. map[2:4 4:16 6:36]

C. map[2:8 4:16 6:36]

D. map[2:2 4:4 6:6]

Solution

1. Step 1: Understand the loop and map assignment

   The loop goes through each number in nums and assigns squares[n] = n * n.

2. Step 2: Calculate each square value

   2*2=4, 4*4=16, 6*6=36, so the map stores these pairs.

3. Final Answer:

   map[2:4 4:16 6:36] -> Option B

4. Quick Check:

   Squares map = map with keys and squared values [OK]

Hint: Map keys with squares store n:n*n pairs [OK]

Common Mistakes:

• Confusing keys and values in map
• Multiplying incorrectly
• Expecting slice output instead of map

4. This Go code tries to read a file but has an error. What is the problem?

package main
import (
    "fmt"
    "os"
)
func main() {
    file := os.Open("file.txt")
    defer file.Close()
    fmt.Println("File opened")
}

medium

A. File name should be absolute path

B. Using defer incorrectly

C. Missing error check after os.Open

D. fmt.Println cannot print strings

Solution

1. Step 1: Check os.Open usage

   os.Open returns two values: file and error. The code only assigns one variable.

2. Step 2: Identify missing error handling

   Without checking error, the program may panic if file does not open.

3. Final Answer:

   Missing error check after os.Open -> Option C

4. Quick Check:

   Always check error from os.Open [OK]

Hint: Always assign and check error from os.Open [OK]

Common Mistakes:

• Ignoring error returned by os.Open
• Assuming defer is wrong here
• Thinking file path must be absolute always

5. You want to create a Go program that reads a list of numbers from a file, squares each number, and writes the results to a new file. Which approach best combines Go features for this task?

hard

A. Use fmt.Println to read and write files directly

B. Use net/http to read files and fmt.Scan to write

C. Use math.Pow to read files and os.Remove to write

D. Use os.Open to read, loop to square, and os.Create with WriteString to save

Solution

1. Step 1: Reading numbers from a file

   os.Open opens the file for reading; then you can scan or read lines.

2. Step 2: Processing and writing results

   Loop through numbers, square them, then use os.Create to create output file and WriteString or similar to write results.

3. Final Answer:

   Use os.Open to read, loop to square, and os.Create with WriteString to save -> Option D

4. Quick Check:

   File read + process + write = os.Open + loop + os.Create [OK]

Hint: Read with os.Open, write with os.Create, process in loop [OK]

Common Mistakes:

• Using fmt.Println for file I/O
• Confusing math.Pow with file reading
• Using network packages for file tasks