concurrency - Why does the use of an unbuffered channel in the same goroutine result in a deadlock?

Question

I'm sure that there is a simple explanation to this trivial situation, but I'm new to the go concurrency model.

when I run this example

package main

import "fmt"

func main() {
    c := make(chan int)    
    c <- 1   
    fmt.Println(<-c)
}

I get this error :

fatal error: all goroutines are asleep - deadlock!

goroutine 1 [chan send]:
main.main()
    /home/tarrsalah/src/go/src/github.com/tarrsalah/tour.golang.org/65.go:8 +0x52
exit status 2

Why ?

---

Wrapping c <- in a goroutine makes the example run as we expected

package main

import "fmt"

func main() {
    c := make(chan int)        
    go func(){
       c <- 1
    }()
    fmt.Println(<-c)
}

Again, why ?

Please, I need deep explanation , not just how to eliminate the deadlock and fix the code.

Answer 1

Waitting for answers