Sample
Handle singleflight DoChan per-caller buffered channels, unclosed channel semantics, abandoned consumer non-blocking delivery, and sync Do coexistence
sha256:079d540812c58ea64c9a9a6abc30c8f6004f9091c641162eeacb224cfd8db43b
PUBLISHED
L3_CONTRACT_PASS
MIT-0
Execution evidence
Declared environment and signed verification runs are separated so you can see exactly what this sample proves.
Evidence basisSigned contract pass
Verification receipts1
Verification levelL3_CONTRACT_PASS
Declared environment
- Execution context
- go
- Operating system
- linux
- Architecture
- x64
- Runtime
- go
- Language
- go
- Package manager
- gomod
Verification-run environments
- Execution context
- go 1.26
- Operating system
- linux alpine · musl
- Architecture
- x64
- Runtime
- go 1.26
- Language
- go
- Package manager
- gomod
- Execution
- container · docker
CONTAINER_RUN · compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS · golang@1 · 2026-08-17
Case
- Goal
- Handle singleflight DoChan per-caller buffered channels, unclosed channel semantics, abandoned consumer non-blocking delivery, and sync Do coexistence HOW
- Packages
-
golang.org/x/sync 0.22.0
- Environment
- go
- Created
- 2026-08-17T20:38:05Z
Commonly assumed
singleflight.Group.DoChan returns a shared broadcast channel that closes after sending, blocks the worker if an abandoned caller stops receiving, and does not deduplicate against synchronous Do.
The sample's author recorded this as what a developer or model would expect here. The contract below is what actually ran.
Contract
- assert singleflight.Group.DoChan allocates a distinct buffered channel of capacity 1 for each caller so concurrent readers do not compete or consume each other's results
- assert a consumer abandoning a DoChan channel due to context timeout does not block the worker goroutine from delivering results to remaining active callers
- assert the channel returned by DoChan remains open after sending a single Result rather than closing upon completion
- assert synchronous Do and asynchronous DoChan share the same in-flight execution registry on a common key and both observe Shared=true
- assert runtime.Goexit in the leader function propagates runtime.Goexit to duplicate callers waiting in synchronous Do rather than returning zero values
Files
- NOTES.md
- contract_test.go
- csx.json
- go.mod
- go.sum
Download the source artifact (tar.gz)
Origin Seeder
csx-seed
Verification receipts
- go 1.26 · linux alpine/x64 · docker · CONTAINER_RUN · compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS · golang@1 · 2026-08-17 · ed25519:d91480838ac982c9