$ # == 1. Prepare your annotated model source code ================================
$ cat <<"EOF" > /tmp/sample.go
package sample

// User is a user model struct.
//
//pgddl:table "users"
//pgddl:constraint UNIQUE ("username")
//pgddl:index "index_users_username" ON "users" ("username")
type User struct {
    UserID   string `db:"user_id"  pgddl:"TEXT NOT NULL" pk:"true"`
    Username string `db:"username" pgddl:"TEXT NOT NULL"`
    Age      int    `db:"age"      pgddl:"INT  NOT NULL"`
}

// Group is a group model struct.
//
//pgddl:table CREATE TABLE IF NOT EXISTS "groups"
//pgddl:index CREATE UNIQUE INDEX "index_groups_group_name" ON "groups" ("group_name")
type Group struct {
    GroupID     string `db:"group_id"    pgddl:"TEXT NOT NULL" pk:"true"`
    GroupName   string `db:"group_name"  pgddl:"TEXT NOT NULL"`
    Description string `db:"description" pgddl:"TEXT NOT NULL"`
}
EOF

$ # == 2. generate DDL ================================
$ ddlgen --dialect postgres --column-tag-go db --ddl-tag-go pgddl --pk-tag-go pk --src /tmp/sample.go --dst /tmp/sample.sql
INFO: 2023/11/16 16:10:39 ddlgen.go:44: source: /tmp/sample.go
INFO: 2023/11/16 16:10:39 ddlgen.go:73: destination: /tmp/sample.sql

$ # == 3. Check generated DDL ================================
$ cat /tmp/sample.sql
-- Code generated by ddlgen. DO NOT EDIT.
--

-- source: tmp/sample.go:5
-- User is a user model struct.
--
-- pgddl:table "users"
-- pgddl:constraint UNIQUE ("username")
CREATE TABLE "users" (
    "user_id"  TEXT NOT NULL,
    "username" TEXT NOT NULL,
    "age"      INT  NOT NULL,
    PRIMARY KEY ("user_id"),
    UNIQUE ("username")
);

-- source: tmp/sample.go:7
-- pgddl:index "index_users_username" ON "users" ("username")
CREATE INDEX "index_users_username" ON "users" ("username");

-- source: tmp/sample.go:16
-- Group is a group model struct.
--
-- pgddl:table CREATE TABLE IF NOT EXISTS "groups"
CREATE TABLE IF NOT EXISTS "groups" (
    "group_id"    TEXT NOT NULL,
    "group_name"  TEXT NOT NULL,
    "description" TEXT NOT NULL,
    PRIMARY KEY ("group_id")
);

-- source: tmp/sample.go:17
-- pgddl:index CREATE UNIQUE INDEX "index_groups_group_name" ON "groups" ("group_name")
CREATE UNIQUE INDEX "index_groups_group_name" ON "groups" ("group_name");

$ ddlgen --help
Usage:
    ddlgen [options]

Description:
    Generate DDL from annotated source code.

options:
    --version (default: false)
        show version information and exit
    --trace (env: DDLGEN_TRACE, default: false)
        trace mode enabled
    --debug (env: DDLGEN_DEBUG, default: false)
        debug mode
    --lang (env: DDLGEN_LANGUAGE, default: go)
        programming language to generate DDL
    --dialect (env: DDLGEN_DIALECT, default: )
        SQL dialect to generate DDL
    --src (env: DDLGEN_SOURCE, default: /dev/stdin)
        source file or directory
    --dst (env: DDLGEN_DESTINATION, default: /dev/stdout)
        destination file or directory
    --column-tag-go (env: DDLGEN_COLUMN_TAG_GO, default: db)
        column annotation key for Go struct tag
    --ddl-tag-go (env: DDLGEN_DDL_TAG_GO, default: ddlgen)
        DDL annotation key for Go struct tag
    --pk-tag-go (env: DDLGEN_PK_TAG_GO, default: pk)
        primary key annotation key for Go struct tag
    --help (default: false)
        show usage