From 75b2beb8482abd56bd46ed52ab8320617adcf57f Mon Sep 17 00:00:00 2001
From: Gabriel Augendre <gabriel@augendre.info>
Date: Wed, 27 Mar 2024 19:53:02 +0100
Subject: [PATCH] add readme

---
 README.md          | 30 ++++++++++++++++++++++++++++++
 contrib/example.go |  2 +-
 2 files changed, 31 insertions(+), 1 deletion(-)
 create mode 100644 README.md

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..4fd1d81
--- /dev/null
+++ b/README.md
@@ -0,0 +1,30 @@
+# foreshadow
+
+`foreshadow` is a Go linter which detects un-shadowed contexts in loops.
+They can lead to performance issues, as documented here: https://gabnotes.org/fat-contexts/
+
+## Example
+
+```go
+package main
+
+import "context"
+
+func ok() {
+	ctx := context.Background()
+
+	for i := 0; i < 10; i++ {
+		ctx := context.WithValue(ctx, "key", i)
+		_ = ctx
+	}
+}
+
+func notOk() {
+	ctx := context.Background()
+
+	for i := 0; i < 10; i++ {
+		ctx = context.WithValue(ctx, "key", i) // "context not shadowed in loop"
+		_ = ctx
+	}
+}
+```
diff --git a/contrib/example.go b/contrib/example.go
index bdbeed1..f8d416b 100644
--- a/contrib/example.go
+++ b/contrib/example.go
@@ -15,7 +15,7 @@ func notOk() {
 	ctx := context.Background()
 
 	for i := 0; i < 10; i++ {
-		ctx = context.WithValue(ctx, "key", i)
+		ctx = context.WithValue(ctx, "key", i) // "context not shadowed in loop"
 		_ = ctx
 	}
 }