Use goreleaser to build and release (#244)

Instead of using gox on one side and an action to release, we can merge
them together with goreleaser which will build for extra targets (arm,
mips if needed in the future) and it also takes care of creating
checksums, a source archive, and a changelog and creating a release with
all the artifacts.

All binaries should respect the old naming convention, so any scripts
out there should still work.

Signed-off-by: Itxaka <igarcia@suse.com>

vendor/google.golang.org/grpc/attributes/attributes.go

@@ -19,7 +19,10 @@
 // Package attributes defines a generic key/value store used in various gRPC
 // components.
 //
-// All APIs in this package are EXPERIMENTAL.
+// Experimental
+//
+// Notice: This package is EXPERIMENTAL and may be changed or removed in a
+// later release.
 package attributes
 
 import "fmt"
@@ -50,6 +53,9 @@ func New(kvs ...interface{}) *Attributes {
 // times, the last value overwrites all previous values for that key.  To
 // remove an existing key, use a nil value.
 func (a *Attributes) WithValues(kvs ...interface{}) *Attributes {
+	if a == nil {
+		return New(kvs...)
+	}
 	if len(kvs)%2 != 0 {
 		panic(fmt.Sprintf("attributes.New called with unexpected input: len(kvs) = %v", len(kvs)))
 	}
@@ -66,5 +72,8 @@ func (a *Attributes) WithValues(kvs ...interface{}) *Attributes {
 // Value returns the value associated with these attributes for key, or nil if
 // no value is associated with key.
 func (a *Attributes) Value(key interface{}) interface{} {
+	if a == nil {
+		return nil
+	}
 	return a.m[key]
 }