TUN-3375: Upgrade coredns and prometheus dependencies

vendor/github.com/opentracing/opentracing-go/log/util.go

@@ -1,6 +1,9 @@
 package log
 
-import "fmt"
+import (
+	"fmt"
+	"reflect"
+)
 
 // InterleavedKVToFields converts keyValues a la Span.LogKV() to a Field slice
 // a la Span.LogFields().
@@ -46,6 +49,10 @@ func InterleavedKVToFields(keyValues ...interface{}) ([]Field, error) {
 		case float64:
 			fields[i] = Float64(key, typedVal)
 		default:
+			if typedVal == nil || (reflect.ValueOf(typedVal).Kind() == reflect.Ptr && reflect.ValueOf(typedVal).IsNil()) {
+				fields[i] = String(key, "nil")
+				continue
+			}
 			// When in doubt, coerce to a string
 			fields[i] = String(key, fmt.Sprint(typedVal))
 		}