[Go] Add Go bindings for ONNX Runtime C API

[dannyota]

Description

Official Go bindings for the ONNX Runtime C API via CGO, following
the pattern of existing language bindings (rust/, java/, csharp/).

Closes #9786

Motivation

Go is widely used for backend services that need ML inference
(embeddings, classification, NLP). There is strong community demand
(#9786, 19 comments) and no official Go support. This PR fills that gap.

What's included

• Session management: create from file or byte buffer, introspect
  inputs/outputs with dynamic dimension support
• Tensor I/O: generic CreateTensor[T] (Go 1.18+ generics),
  untyped NewTensorFromBytes, string tensors, zero-length dimensions
• Session options: thread counts, graph optimization, execution mode,
  memory arena, profiling, free dimension overrides
• Execution providers: CUDA (V2), TensorRT (V2), generic string
  key-value API for all other EPs
• IO Binding: bind inputs/outputs to devices for GPU workflows
• Model metadata: producer, graph name, domain, version, custom keys
• Run options: log level, tag, config entries
• Cancellation: context.Context support via RunOptionsSetTerminate
• Concurrency: Session.Run safe for concurrent use (ORT guarantee)
• Sequence/Map: value type inspection and sequence element access

Design

Wraps the C API vtable (OrtApi) through ~80 C shim functions in
cshim.h/cshim.c — CGO cannot call C function pointers directly.
Library loaded at runtime via dlopen (Linux/macOS) or LoadDLL
(Windows). Singleton OrtEnv per process via sync.Mutex.

Zero-copy tensor inputs via runtime.Pinner. Output tensors wrap
ORT-allocated memory with views valid until Close().

Module path: github.com/microsoft/onnxruntime/go
Package: onnxruntime (import as ort)
Go 1.26 minimum. stdlib + CGO only — no third-party dependencies.

Tests

46 tests passing with -race:

• Lifecycle, inference correctness, dynamic shapes, zero-length dims
• All tensor types (float32, int64, bool, string, bytes, scalars)
• Error handling, type/shape mismatch, use-after-close
• Concurrency: 16 goroutines × 50 runs on one session
• Context cancellation, IO binding, model metadata, run options
• Integration: Qwen3-Embedding-0.6B ONNX INT8 (59 inputs, 57 outputs)
• Semgrep Pro: 0 findings (195 rules)
• golangci-lint: 0 issues

[dannyota]

@microsoft-github-policy-service agree

[dannyota]

Updated with a second commit:

• Fixed TOCTOU race in NewIOBinding (use-after-free on concurrent Close)
• Fixed empty outputNames panic in Run/RunWithOptions
• Fixed metadata use-after-close segfault
• Added 15 tests (63 total), covering all tensor types, error paths, IO binding, and edge cases
• Bumped minimum ORT to 1.27.0 for GetMemPatternEnabled/GetSessionExecutionMode getters
• Tested against ORT 1.28.0 built from rel-1.28.0 branch — all passing

[dannyota]

Added API version fallback: bindings now try API version 27 first, fall back to 17 for older ORT libraries. This means ORT 1.17+ is supported (previously required 1.27+). The two getter functions added in 1.27 (GetExecutionMode, IsMemPatternEnabled) return a clear error on older libraries instead of crashing.