What Is New in Go 1.7
Go 1.7 brings a refined compiler, a more efficient garbage collector, and significant standard library additions. The focus is on performance and providing better tools for writing concurrent servers.
| Category | Key Changes |
|---|---|
| Language | No changes to the language specification. |
| Tools | SSA backend for x86-64, improved `go vet` checks. |
| Performance | Up to 20% speedups, lower GC latency. |
| Standard Library | New `context` package, `httptrace`, and `HTTP/2` push support. |
How did the compiler and performance improve?
The new SSA-based compiler backend for x86-64 is the star of the show. It generates better, more optimized code, which is why we're seeing those impressive 5-35% CPU reductions across the board. This is a foundational change that pays off in every binary you build.
The garbage collector got a serious latency reduction. By running parts of the GC concurrently, it significantly shortens the dreaded "stop-the-world" pauses. For servers handling live requests, this means smoother performance and more consistent response times.
What's the deal with the new context package?
The context package was promoted from x/net/context to the standard library,
solidifying its role as the standard way to handle cancellation and timeouts in concurrent operations. This move
was a big deal for anyone writing servers, APIs, or any distributed logic.
In practice, it meant we could finally pass request-scoped values, cancellation signals, and deadlines through
our call stacks without inventing our own patterns. The standard library itself adopted it, with
net/http using context in Request right out of the box.
What new tools did we get for HTTP?
Go 1.7 beefed up its HTTP toolkit considerably. The httptrace package provides hooks to monitor a
client request's lifecycle-perfect for debugging latency issues and seeing where time is spent during DNS
lookups, connection dialing, and TLS handshakes.
On the server side, the new ResponseController type unlocked HTTP/2 Server Push, allowing you to
proactively send resources to the client. This was a forward-looking feature for optimizing web application
performance.
Were there any subtle but important changes?
Absolutely. The go vet tool got smarter, adding new checks for things like malformed printf-style
verbs and method signatures that don't match interface expectations. These are the kinds of fixes that catch
bugs early without slowing you down.
The testing package also introduced a Subtest and Subbenchmark feature. This let us
structure table-driven tests more cleanly and run specific subsets of tests, which is a huge quality-of-life
improvement for large test suites.
FAQ
Is the SSA backend available for all architectures?
No, in Go 1.7, the SSA backend is only
for 64-bit x86 systems (linux/amd64, darwin/amd64, freebsd/amd64, and
windows/amd64). Support for other architectures came in later releases.
Do I need to change my code to use the new context package?
If you were already using
golang.org/x/net/context, the change is minimal. You can do a find-and-replace to use the new
context import path. The API is identical.
How significant are the real-world performance gains?
It depends on your workload. Benchmarks
showed CPU improvements between 5% and 35%. The most noticeable difference for many was the reduced GC latency,
leading to fewer application pauses.
Can I use HTTP/2 Server Push with the standard http.Handler?
Yes, but you need to use the new
ResponseController type to access the underlying http.Pusher interface. It's a few
extra lines of code to enable push capabilities for a response.
What happens if my printf format strings are wrong?
The improved go vet tool
will now catch a wider range of printf formatting errors at build time. This prevents runtime panics from
mismatched format specifiers and arguments.