Unreachable code

Unreachable code is code that can never be executed and is a logical kind of error. As the Go compiler itself cannot catch such logical errors, you will need to use the go tool vet command to help.

The example code in this section is saved as cannotReach.go and can be divided into two parts.

The first part has the following Go code:

package main 
 
import ( 
   "fmt" 
) 


func x() int {

 
   return -1 
   fmt.Println("Exiting x()") 
   return -1 
} 
 
func y() int { 
   return -1 
   fmt.Println("Exiting y()") 
   return -1 
} 

The second part is as follows:

func main() { 
   fmt.Println(x()) 
   fmt.Println("Exiting program...") 
} 

As you can see, the unreachable code is in the first part. Both x() and y() functions have unreachable code because their return statements were put at the wrong place. However, we are not done yet because we will have to let the go tool vet tool discover the unreachable code. The process is simple and includes the execution of the following command:

$ go tool vet cannotReach.go
cannotReach.go:9: unreachable code
cannotReach.go:14: unreachable code
 

Additionally, you can see that go tool vet detects unreachable code even if the surrounding function is not going to be executed at all, as happens with y().