build: add build constraint to restrict promslog to go1.21+

We still support go1.20 in the test matrix, but slog was only added to the go standard library in go1.21. The build constraints allow us to continue supporting go1.20 for the rest of the existing library, at the cost of only supporting promslog for go1.21+. Signed-off-by: TJ Hoplock <[email protected]>
prometheus · Aug 17, 2024 · c3622e1 · c3622e1
1 parent 8e18295
commit c3622e1
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diff --git a/promslog/flag/flag.go b/promslog/flag/flag.go
@@ -15,6 +15,8 @@
 // across Prometheus components.
 // It should typically only ever be imported by main packages.
 
+//go:build go1.21
+
 package flag
 
 import (

diff --git a/promslog/slog.go b/promslog/slog.go
@@ -14,6 +14,9 @@
 // Package promslog defines standardised ways to initialize the Go standard
 // library's log/slog logger.
 // It should typically only ever be imported by main packages.
+
+//go:build go1.21
+
 package promslog
 
 import (

diff --git a/promslog/slog_test.go b/promslog/slog_test.go
@@ -11,6 +11,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+//go:build go1.21
+
 package promslog
 
 import (