diff --git a/data/README.md b/data/README.md
new file mode 100644
index 0000000..45220ad
--- /dev/null
+++ b/data/README.md
@@ -0,0 +1,7 @@
+## Updating `data`
+
+1. Go to [https://github.com/PrismarineJS/minecraft-data/tree/master/data/pc/{version}](https://github.com/PrismarineJS/minecraft-data/tree/master/data/pc)
+2. Update the URL (if appropriate) in [gen_block.go](block/gen_block.go), [gen_entity.go](entity/gen_entity.go),
+[gen_item.go](item/gen_item.go), and [gen_packetid.go](packetid/gen_packetid.go)
+3. Update the `URL` in [gen_soundid.go](soundid/gen_soundid.go)
+4. Run `go generate ./...`
\ No newline at end of file
diff --git a/data/block/gen_blocks.go b/data/block/gen_block.go
similarity index 85%
rename from data/block/gen_blocks.go
rename to data/block/gen_block.go
index afac604..f02f92f 100644
--- a/data/block/gen_blocks.go
+++ b/data/block/gen_block.go
@@ -130,7 +130,8 @@ func makeBlockDeclaration(blocks []Block) *ast.DeclStmt {
 	return out
 }
 
-//go:generate go run $GOFILE > ./packetid.go
+//go:generate go run $GOFILE
+//go:generate go fmt block.go
 func main() {
 	blocks, err := downloadInfo()
 	if err != nil {
@@ -138,7 +139,14 @@ func main() {
 		os.Exit(1)
 	}
 
-	fmt.Println(`// Code generated by gen_blocks.go; DO NOT EDIT.
+	f, err := os.Create("entity.go")
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+		os.Exit(1)
+	}
+	defer f.Close()
+
+	fmt.Fprintln(f, `// Code generated by gen_blocks.go; DO NOT EDIT.
 
 // Package block stores information about blocks in Minecraft.
 package block
@@ -176,26 +184,26 @@ type Block struct {
 `)
 	format.Node(os.Stdout, token.NewFileSet(), makeBlockDeclaration(blocks))
 
-	fmt.Println()
-	fmt.Println()
-	fmt.Println("// ByID is an index of minecraft blocks by their ID.")
-	fmt.Println("var ByID = map[ID]*Block{")
+	fmt.Fprintln()
+	fmt.Fprintln()
+	fmt.Fprintln(f, "// ByID is an index of minecraft blocks by their ID.")
+	fmt.Fprintln(f, "var ByID = map[ID]*Block{")
 	for _, b := range blocks {
-		fmt.Printf("  %d: &%s,\n", b.ID, strcase.ToCamel(b.Name))
+		fmt.Fprintf(f,"  %d: &%s,\n", b.ID, strcase.ToCamel(b.Name))
 	}
-	fmt.Println("}")
+	fmt.Fprintln(f, "}")
 
-	fmt.Println()
-	fmt.Println("// StateID maps all possible state IDs to a corresponding block ID.")
-	fmt.Println("var StateID = map[uint32]ID{")
+	fmt.Fprintln()
+	fmt.Fprintln(f, "// StateID maps all possible state IDs to a corresponding block ID.")
+	fmt.Fprintln(f, "var StateID = map[uint32]ID{")
 	for _, b := range blocks {
 		if b.MinStateID == b.MaxStateID {
-			fmt.Printf("  %d: %d,\n", b.MinStateID, b.ID)
+			fmt.Fprintf(f, "  %d: %d,\n", b.MinStateID, b.ID)
 		} else {
 			for i := b.MinStateID; i <= b.MaxStateID; i++ {
-				fmt.Printf("  %d: %d,\n", i, b.ID)
+				fmt.Fprintf(f, "  %d: %d,\n", i, b.ID)
 			}
 		}
 	}
-	fmt.Println("}")
+	fmt.Fprintln("}")
 }
diff --git a/data/entity/gen/gen_entity.go b/data/entity/gen_entity.go
similarity index 97%
rename from data/entity/gen/gen_entity.go
rename to data/entity/gen_entity.go
index 6a6603d..6df50ed 100644
--- a/data/entity/gen/gen_entity.go
+++ b/data/entity/gen_entity.go
@@ -1,5 +1,6 @@
-// gen_entity.go generates entity information.
+//+build ignore
 
+// gen_entity.go generates entity information.
 package main
 
 import (
@@ -106,7 +107,7 @@ func makeEntityDeclaration(entities []Entity) *ast.DeclStmt {
 }
 
 //go:generate go run $GOFILE
-//go:generate go fmt ../entity.go
+//go:generate go fmt entity.go
 func main() {
 	entities, err := downloadInfo()
 	if err != nil {
@@ -114,7 +115,7 @@ func main() {
 		os.Exit(1)
 	}
 
-	f, err := os.Create("../entity.go")
+	f, err := os.Create("entity.go")
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
 		os.Exit(1)
diff --git a/data/item/gen_item.go b/data/item/gen_item.go
index 0a1286d..32850c8 100644
--- a/data/item/gen_item.go
+++ b/data/item/gen_item.go
@@ -1,7 +1,6 @@
-// gen_blocks.go generates block information.
-
 //+build ignore
 
+// gen_item.go generates item information.
 package main
 
 import (
diff --git a/data/lang/downloader.go b/data/lang/downloader.go
index 1f06f38..63f6e1e 100644
--- a/data/lang/downloader.go
+++ b/data/lang/downloader.go
@@ -1,8 +1,11 @@
-// This program can automatic download language.json file and convert into .go
+//+build ignore
+
+// This program can automatically download language.json file and convert into .go
 package main
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"log"
@@ -27,12 +30,11 @@ func main() {
 		readLang("en_us", f)
 		return
 	}
-	// Pseudo code for get versionURL:
-	// $manifest = {https://launchermeta.mojang.com/mc/game/version_manifest.json}
-	// $latest = $manifest.latest.release
-	// $version = {$manifest.versions[where .id == $latest ].url}
-	// $versionURL = $version.assetIndex.url
-	versionURL := "https://launchermeta.mojang.com/v1/packages/e5af543d9b3ce1c063a97842c38e50e29f961f00/1.17.json"
+
+	versionURL, err := assetIndexURL()
+	if err != nil {
+		log.Fatal(err)
+	}
 	log.Print("start generating lang packages")
 
 	resp, err := http.Get(versionURL)
@@ -155,3 +157,59 @@ func trans(m map[string]string) {
 		}
 	}
 }
+
+func assetIndexURL() (string, error) {
+	// Pseudo code for get versionURL:
+	// $manifest = {https://launchermeta.mojang.com/mc/game/version_manifest.json}
+	// $latest = $manifest.latest.release
+	// $versionURL = {$manifest.versions[where .id == $latest ].url}
+	// $assetIndexURL = $version.assetIndex.url
+	var manifest struct {
+		Latest struct {
+			Release string `json:"release"`
+		} `json:"latest"`
+		Versions []struct{
+			ID string `json:"id"`
+			URL string `json:"url"`
+		} `json:"versions"`
+	}
+
+	manifestRes, err := http.Get("https://launchermeta.mojang.com/mc/game/version_manifest.json")
+	if err != nil {
+		return "", fmt.Errorf("could not reach version manifest: %w", err)
+	}
+	defer manifestRes.Body.Close()
+
+	if err := json.NewDecoder(manifestRes.Body).Decode(&manifest); err != nil {
+		return "", fmt.Errorf("could not decode manifest JSON: %w", err)
+	}
+
+	var versionURL string
+	for _, v := range manifest.Versions {
+		if strings.EqualFold(manifest.Latest.Release, v.ID) {
+			versionURL = v.URL
+			break
+		}
+	}
+	if versionURL == "" {
+		return "", errors.New("could not determine versionURL")
+	}
+
+	var version struct{
+		AssetIndex struct{
+			URL string `json:"url"`
+		} `json:"assetIndex"`
+	}
+
+	versionRes, err := http.Get(versionURL)
+	if err != nil {
+		return "", fmt.Errorf("could not reach versionURL: %w", err)
+	}
+	defer versionRes.Body.Close()
+
+	if err := json.NewDecoder(versionRes.Body).Decode(&version); err != nil {
+		return "", fmt.Errorf("could not decode version JSON: %w", err)
+	}
+
+	return version.AssetIndex.URL, nil
+}
diff --git a/data/packetid/gen/gen_packetIDs.go b/data/packetid/gen_packetid.go
similarity index 96%
rename from data/packetid/gen/gen_packetIDs.go
rename to data/packetid/gen_packetid.go
index f0ec74a..511098b 100644
--- a/data/packetid/gen/gen_packetIDs.go
+++ b/data/packetid/gen_packetid.go
@@ -1,4 +1,6 @@
-// gen_packetIDs.go generates the enumeration of packet IDs used on the wire.
+//+build ignore
+
+//gen_packetid.go generates the enumeration of packet IDs used on the wire.
 package main
 
 import (
@@ -161,7 +163,7 @@ func downloadInfo() (*protocolIDs, error) {
 }
 
 //go:generate go run $GOFILE
-//go:generate go fmt ../packetid.go
+//go:generate go fmt packetid.go
 func main() {
 	pIDs, err := downloadInfo()
 	if err != nil {
@@ -169,7 +171,7 @@ func main() {
 		os.Exit(1)
 	}
 
-	f, err := os.Create("../packetid.go")
+	f, err := os.Create("packetid.go")
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
 		os.Exit(1)
diff --git a/data/soundid/gen_soundIDs.go b/data/soundid/gen_soundid.go
similarity index 93%
rename from data/soundid/gen_soundIDs.go
rename to data/soundid/gen_soundid.go
index 32038f7..bd0ce0c 100644
--- a/data/soundid/gen_soundIDs.go
+++ b/data/soundid/gen_soundid.go
@@ -1,6 +1,6 @@
 //+build ignore
 
-// gen_soundIDs.go generates the enumeration of sound IDs.
+// gen_soundid.go generates the enumeration of sound IDs.
 package main
 
 import (
@@ -12,7 +12,7 @@ import (
 )
 
 const (
-	protocolURL = "https://pokechu22.github.io/Burger/1.17.1.json"
+	URL = "https://pokechu22.github.io/Burger/1.17.1.json"
 )
 
 type sound struct {
@@ -61,7 +61,7 @@ func main() {
 }
 
 func downloadSoundInfo() ([]sound, error) {
-	resp, err := http.Get(protocolURL)
+	resp, err := http.Get(URL)
 	if err != nil {
 		return nil, err
 	}