Lift Go read steps to taint steps

Author: owen-mc

go/ql/lib/semmle/go/dataflow/internal/TaintTrackingUtil.qll

@@ -96,6 +96,7 @@ private predicate localAdditionalForwardTaintStep(
     pred2 = pred.(DataFlow::PostUpdateNode).getPreUpdateNode()
   |
     referenceStep(pred2, succ) or
+    DataFlowPrivate::readStep(pred2, _, succ) or
     elementWriteStep(pred2, succ) or
     fieldReadStep(pred2, succ) or
     elementStep(pred2, succ) or

go/ql/test/library-tests/semmle/go/dataflow/FlowSteps/LocalTaintStep.expected

@@ -11,6 +11,7 @@
 | main.go:47:2:50:2 | next range element | main.go:47:2:50:2 | extract:0 range element |
 | main.go:47:2:50:2 | next range element | main.go:47:2:50:2 | extract:1 range element |
 | main.go:47:20:47:21 | xs | main.go:47:2:50:2 | extract:1 range element |
+| main.go:57:4:57:5 | ch | main.go:57:2:57:5 | <-... |
 | strings.go:9:24:9:24 | s | strings.go:9:8:9:38 | call to Replace |
 | strings.go:9:32:9:34 | "_" | strings.go:9:8:9:38 | call to Replace |
 | strings.go:10:27:10:27 | s | strings.go:10:8:10:42 | call to ReplaceAll |