What signs indicate that your level of professional competence corresponds to the Middle level?

The Middle level in Go development is usually characterized by the following features:

• Confident mastery of the basics of the language: understanding goroutines, channels, interfaces, structures.
• Ability to independently develop and maintain modules of medium complexity.
• Knowledge of the standard library and the ability to apply it to solve practical problems.
• Experience with version control systems, writing tests (unit, integration).
• Understanding of design principles and patterns, ability to read and improve other people's code.
• Participation in code reviews, ability to give and receive constructive criticism.
• Ability to estimate task completion times and plan your work.

Example: you can write a function that efficiently processes data using goroutines and channels, and also cover it with tests.

func sum(nums []int, c chan int) {
    total := 0
    for _, n := range nums {
        total += n
    }
    c <- total
}

func main() {
    nums := []int{1, 2, 3, 4, 5, 6}
    c := make(chan int)
    go sum(nums[:len(nums)/2], c)
    go sum(nums[len(nums)/2:], c)
    x, y := <-c, <-c
    fmt.Println(x + y) // 21
}