Race Condition Issue : Protect union registry with sync.Map to prevent concurrent write panics (race condition)

[DARSHANR007]

Confirm this is a Go library issue and not an underlying Cloudflare API issue

• This is an issue with the Go library

Describe the Bug

Problem

The union registry (unionRegistry and unionVariants global maps in internal/apijson/registry.go) are unprotected and not thread-safe.

When multiple goroutines call RegisterUnion() simultaneously, the Go runtime panics with:

fatal error: concurrent map writes

The issue occurs because both global maps are written concurrently without synchronization.

---

Vulnerable Code

File: internal/apijson/registry.go

// Lines 15-16: Unprotected maps
var unionRegistry = map[reflect.Type]unionEntry{}
var unionVariants = map[reflect.Type]interface{}{}

// Lines 24-30: Concurrent writes cause panic
func RegisterUnion(typ reflect.Type, discriminator string, variants ...UnionVariant) {
    unionRegistry[typ] = unionEntry{...} // concurrent write
    for _, variant := range variants {
        unionVariants[variant.Type] = typ // concurrent write
    }
}

Multiple goroutines calling RegisterUnion() simultaneously can trigger a runtime panic.

---

Steps To Reproduce

1. Create multiple goroutines that call RegisterUnion() concurrently.
2. Run the race demo test repeatedly.
3. The runtime eventually panics with concurrent map writes.

---

Command

go test ./internal/apijson -run TestBareMapConcurrency -v -count=50

---

Expected Behavior

The registry should support concurrent registration safely without panicking.

Expected approaches could include:

• protecting the maps with sync.RWMutex
• using sync.Map
• or ensuring registration only happens during initialization

---

Actual Output

=== RUN   TestBareMapConcurrency
fatal error: concurrent map writes

goroutine 12 [running]:
runtime/maps.go:1046 +0x18
github.com/cloudflare/cloudflare-go/v7/internal/apijson.TestBareMapConcurrency.func1(0x5)
    internal/apijson/registry_race_demo_test.go:138 +0x128

Process exit code: 2

---

Error

fatal error: concurrent map writes

---

Environment

OS

Windows/amd64

Go Version

Go 1.22.0

Library Version

github.com/cloudflare/cloudflare-go/v7