feat: agent metadata with custom collectors

internal/agent/metadata/collector/shell/collector.go

@@ -0,0 +1,46 @@
+package shell
+
+import (
+	"bytes"
+	"context"
+	"os"
+	"os/exec"
+	"strings"
+
+	"forge.cadoles.com/Cadoles/emissary/internal/agent/metadata"
+	"github.com/pkg/errors"
+)
+
+type Collector struct {
+	name    string
+	command string
+	args    []string
+}
+
+// Collect implements agent.MetadataCollector
+func (c *Collector) Collect(ctx context.Context) (string, string, error) {
+	cmd := exec.CommandContext(ctx, c.command, c.args...)
+
+	var buf bytes.Buffer
+
+	cmd.Stdout = &buf
+	cmd.Stderr = os.Stderr
+
+	if err := cmd.Run(); err != nil {
+		return "", "", errors.WithStack(err)
+	}
+
+	value := strings.TrimSpace(buf.String())
+
+	return c.name, value, nil
+}
+
+func NewCollector(name string, command string, args ...string) *Collector {
+	return &Collector{
+		name:    name,
+		command: command,
+		args:    args,
+	}
+}
+
+var _ metadata.Collector = &Collector{}