Go by Example: Recover
+ +|
+ A |
+ + + + | +
| + + | +
+  
+ package main
+ |
+
| + + | +
+
+ import (
+ "fmt"
+)
+ |
+
| + + | +
+
+ func main() {
+ |
+
| + + | +
+
+ recoverFromBuiltInPanic(10)
+ |
+
| + + | +
+
+ fmt.Println()
+ |
+
| + + | +
+
+ recoverFromCustomPanic(-1)
+}
+ |
+
|
+ defer is defined. + + |
+
+
+ func recoverFromBuiltInPanic(i int) {
+ |
+
| + + | +
+
+ defer func() {
+ if r := recover(); r != nil {
+ fmt.Println("Recovered. Error:\n", r)
+ }
+ }()
+ |
+
| + + | +
+
+ var a [5]int
+ fmt.Printf("Getting index %d"+
+ " of array of len %d...\n", i, len(a))
+ fmt.Printf("Item in index %d: %d", i, a[i])
+}
+ |
+
|
+ defer is defined. + + |
+
+
+ func recoverFromCustomPanic(i int) {
+ |
+
| + + | +
+
+ defer func() {
+ if r := recover(); r != nil {
+ fmt.Println("Recovered. Error:\n", r)
+ }
+ }()
+ |
+
| + + | +
+
+ fmt.Printf("About to process i=%d\n", i)
+ |
+
| + + | +
+
+ if i < 0 {
+ panic(fmt.Errorf("Accepting only"+
+ " non-negative numbers but received %d", i))
+ }
+ |
+
| + + | +
+
+ fmt.Printf("Doing something with %d\n", i)
+}
+ |
+
|
+ Running this program will exit correctly, +even though panic was invoked in two methods. +The recover is responsible for recovering from panics. + + |
+
+
+ $ go run recover.go
+Getting index 10 of array of len 5...
+Recovered. Error:
+ runtime error: index out of range [10] with length 5
+ |
+
|
+ Note that, in Go it is idiomatic +to use error-indicating return values wherever possible. + + |
+
+
+ About to process i=-1
+Recovered. Error:
+ Accepting only non-negative numbers but received -1
+ |
+
+ Next example: Collection Functions. +
+ + +