Support for experiment env vars (#1214)

* feat: experiments env var handling

* feat: read experiments from dotenv files

* docs: removed experimental cli flags

* feat: use vars instead of struct with reflection

internal/experiments/experiments.go

@@ -0,0 +1,43 @@
+package experiments
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/joho/godotenv"
+)
+
+const envPrefix = "TASK_X_"
+
+var TestExperiment bool
+
+func init() {
+	if err := readDotEnv(); err != nil {
+		panic(err)
+	}
+	TestExperiment = parseEnv("TestExperiment")
+}
+
+func parseEnv(xName string) bool {
+	envName := fmt.Sprintf("%s%s", envPrefix, xName)
+	return os.Getenv(envName) == "1"
+}
+
+func readDotEnv() error {
+	env, err := godotenv.Read()
+	if errors.Is(err, os.ErrNotExist) {
+		return nil
+	}
+	if err != nil {
+		return err
+	}
+	// If the env var is an experiment, set it.
+	for key, value := range env {
+		if strings.HasPrefix(key, envPrefix) {
+			os.Setenv(key, value)
+		}
+	}
+	return nil
+}