Go Channels behaviour that i do not understand

Question

I recently started learning Go and there is a case that i have been written that i cannot understand why does he get two different behaviors based on a change made in a single line that just prints [line 13],

In the first run i run the program with [line 13] and then in the main routine when i print the length of the channel at [line 21] that print 0 and in the next line thats just come after that its print 2 (I'm talking about the first print that the main routine made).

In the second run i removed [line 13] and then in both prints in the first time that print thats the length of the channel is 2.

in the picture you can see in the console the two diffrents prints that i dont understand why they are different [just because add/remove line 13].

// Go behavior that I do not understand /:
package main

import "fmt"

func main() {

    mychnl := make(chan string, 2)

    go func(input chan string) {
        input <- "Inp1"
        // If we remove this line the length of the chan in the print will be equal in both prints
        fmt.Println("Tell me why D:")
        input <- "Inp2"
        input <- "Inp3"
        input <- "Inp4"
        close(input)
    }(mychnl)

    for res := range mychnl {
        fmt.Printf("Length of the channel is: %v The received value is: %s length need to be == ", len(mychnl), res)
        fmt.Println(len(mychnl))
    }
}

/*
Output ->
Line 13 = fmt.Println("Tell me why D:")

First run with line 13:
Tell me why D:
Length of the channel is: 0 The received value is: Inp1 length need to be == 2
Length of the channel is: 2 The received value is: Inp2 length need to be == 2
Length of the channel is: 1 The received value is: Inp3 length need to be == 1
Length of the channel is: 0 The received value is: Inp4 length need to be == 0

Second run without line 13:
Length of the channel is: 2 The received value is: Inp1 length need to be == 2
Length of the channel is: 2 The received value is: Inp2 length need to be == 2
Length of the channel is: 1 The received value is: Inp3 length need to be == 1
Length of the channel is: 0 The received value is: Inp4 length need to be == 0
*/