Goroutine creation - Step-by-Step Execution

Concept Flow - Goroutine creation

Start main function

↓

Create goroutine

↓

Goroutine runs concurrently

↓

Main continues execution

↓

Wait or finish main

↓

Program ends

The main function starts, creates a goroutine that runs concurrently, then continues. The program ends when main finishes.

Execution Sample

Go

package main
import "fmt"
func sayHello() {
    fmt.Println("Hello from goroutine")
}
func main() {
    go sayHello()
    fmt.Println("Hello from main")
}

This code creates a goroutine to run sayHello concurrently while main prints its own message.

Execution Table

Step	Action	Evaluation	Result
1	Start main function	main starts	Ready to run code
2	Create goroutine with go sayHello()	sayHello scheduled	sayHello runs concurrently
3	Execute fmt.Println("Hello from main")	Print main message	Output: Hello from main
4	Goroutine runs sayHello()	Print goroutine message	Output: Hello from goroutine
5	Main function ends	Program ends	Program terminates

💡 Main function ends, program terminates, goroutine may finish before or after main prints

Variable Tracker

Variable	Start	After goroutine creation	After main print	Final
sayHello goroutine	Not started	Scheduled to run	Running or finished	Finished
main function	Running	Running	Running	Finished

Key Moments - 2 Insights

Why might the goroutine's print appear before or after the main print?

Because goroutines run concurrently, their execution order is not guaranteed. See execution_table steps 3 and 4 where outputs can appear in any order.

What happens if main ends before the goroutine runs?

The program ends immediately, stopping all goroutines. So the goroutine might not print if main finishes too soon, as shown in execution_table step 5.

Visual Quiz - 3 Questions

Look at the execution_table, what is printed at step 3?

A Hello from goroutine

B Hello from main

C No output

D Program ends

💡 Hint

Check the 'Result' column at step 3 in execution_table

At which step does the goroutine start running?

A Step 1

B Step 2

C Step 4

D Step 3

💡 Hint

Look for when sayHello prints in execution_table

If main ends immediately after creating the goroutine, what might happen?

A Goroutine might not run at all

B Goroutine definitely prints first

C Program waits for goroutine to finish

D Main prints twice

💡 Hint

See key_moments about program ending before goroutine runs

Concept Snapshot

Goroutine creation in Go:
- Use 'go' keyword before a function call
- Starts function concurrently
- Main continues without waiting
- Program ends when main finishes
- Goroutine may not complete if main ends early

Full Transcript

This example shows how a goroutine is created in Go using the 'go' keyword before a function call. The main function starts and creates a goroutine that runs the sayHello function concurrently. The main function then prints its own message. Because goroutines run at the same time as main, their output order can vary. If main ends before the goroutine runs, the program stops immediately and the goroutine may not print. This trace shows each step: starting main, creating the goroutine, printing from main, printing from the goroutine, and ending the program.