Renaming OTEL_RESOURCE_LABELS env var

As per the specification here open-telemetry/opentelemetry-specification#758

Author: Alex Boten

sdk/resource/doc.go

@@ -22,7 +22,7 @@
 // the Detect function to generate a Resource from the merged information.
 //
 // To load a user defined Resource from the environment variable
-// OTEL_RESOURCE_LABELS the FromEnv Detector can be used. It will interpret
+// OTEL_RESOURCE_ATTRIBUTES the FromEnv Detector can be used. It will interpret
 // the value as a list of comma delimited key/value pairs
 // (e.g. `<key1>=<value1>,<key2>=<value2>,...`).
 package resource

sdk/resource/env.go

@@ -24,7 +24,7 @@ import (
 )
 
 // envVar is the environment variable name OpenTelemetry Resource information can be assigned to.
-const envVar = "OTEL_RESOURCE_LABELS"
+const envVar = "OTEL_RESOURCE_ATTRIBUTES"
 
 var (
 	//errMissingValue is returned when a resource value is missing.