feat: parse ENV Variables in json file

.gitignore

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+.idea

README.md

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+# jenv
+
+`jenv` is a Go package that simplifies configuration parsing by allowing placeholders in JSON and YAML files to be resolved dynamically using environment variables. The package supports default values and type-safe conversion of fields.
+
+## Features
+* Parse JSON and YAML configurations with environment variable resolution.
+* Support for default values in ${VAR:default} syntax.
+* Type-safe mapping of configuration values to Go structs.
+* Handle complex data types such as time.Time, time.Duration, slices, and maps.
+
+## Installation
+
+> go get github.com/oarkflow/jenv
+
+## Usage
+### Environment Variables
+
+Set environment variables for your configuration:
+
+```bash
+export SERVICE_NAME="MyAppService"
+export ENABLE_SERVICE="true"
+export RATE="2.5"
+export TIMEOUT="15s"
+export START_TIME="2024-01-01T12:00:00Z"
+export DB_HOST="db.example.com"
+export DB_PORT="5432"
+export DB_REPLICA_PORT="5433"
+
+```
+
+## Example JSON Configuration
+Create a JSON configuration file config.json:
+
+```json
+{
+    "service": {
+        "name": "${SERVICE_NAME:DefaultService}",
+        "enabled": "${ENABLE_SERVICE:false}",
+        "timeout": "${TIMEOUT:30s}",
+        "start_time": "${START_TIME:2023-01-01T00:00:00Z}",
+        "rate": "${RATE:1.0}"
+    },
+    "database": {
+        "hosts": ["${DB_HOST:localhost}"],
+        "ports": {
+            "primary": "${DB_PORT:3306}",
+            "replica": "${DB_REPLICA_PORT:3307}"
+        }
+    }
+}
+
+```
+
+Parse it in your Go code:
+
+```go
+package main
+
+import (
+	"fmt"
+	"os"
+	"time"
+
+	"github.com/yourusername/jenv"
+)
+
+type Service struct {
+	Name      string        `json:"name"`
+	Enabled   bool          `json:"enabled"`
+	Rate      float64       `json:"rate"`
+	Timeout   time.Duration `json:"timeout"`
+	StartTime time.Time     `json:"start_time"`
+}
+
+type Database struct {
+	Hosts []string       `json:"hosts"`
+	Ports map[string]int `json:"ports"`
+}
+
+type Config struct {
+	Service  Service  `json:"service"`
+	Database Database `json:"database"`
+}
+
+func main() {
+	os.Setenv("SERVICE_NAME", "MyAppService")
+	os.Setenv("ENABLE_SERVICE", "true")
+	os.Setenv("RATE", "2.5")
+	os.Setenv("TIMEOUT", "15s")
+	os.Setenv("START_TIME", "2024-01-01T12:00:00Z")
+	os.Setenv("DB_HOST", "db.example.com")
+	os.Setenv("DB_PORT", "5432")
+	os.Setenv("DB_REPLICA_PORT", "5433")
+
+	jsonData := []byte(`
+	{
+	    "service": {
+	        "name": "${SERVICE_NAME:DefaultService}",
+	        "enabled": "${ENABLE_SERVICE:false}",
+	        "timeout": "${TIMEOUT:30s}",
+	        "start_time": "${START_TIME:2023-01-01T00:00:00Z}",
+	        "rate": "${RATE:1.0}"
+	    },
+	    "database": {
+	        "hosts": ["${DB_HOST:localhost}"],
+	        "ports": {"primary": "${DB_PORT:3306}", "replica": "${DB_REPLICA_PORT:3307}"}
+	    }
+	}`)
+
+	var config Config
+	err := jenv.UnmarshalJSON(jsonData, &config)
+	if err != nil {
+		fmt.Printf("Error: %v\n", err)
+		return
+	}
+
+	fmt.Printf("Config: %+v\n", config)
+}
+
+```
+
+## Example YAML Configuration
+Create a YAML configuration file config.yaml:
+
+```yaml
+service:
+  name: "${SERVICE_NAME:DefaultService}"
+  enabled: "${ENABLE_SERVICE:false}"
+  timeout: "${TIMEOUT:30s}"
+  start_time: "${START_TIME:2023-01-01T00:00:00Z}"
+  rate: "${RATE:1.0}"
+database:
+  hosts:
+    - "${DB_HOST:localhost}"
+  ports:
+    primary: "${DB_PORT:3306}"
+    replica: "${DB_REPLICA_PORT:3307}"
+
+```
+
+Parse it in your Go code:
+```go
+yamlData := []byte(`
+service:
+  name: "${SERVICE_NAME:DefaultService}"
+  enabled: "${ENABLE_SERVICE:false}"
+  timeout: "${TIMEOUT:30s}"
+  start_time: "${START_TIME:2023-01-01T00:00:00Z}"
+  rate: "${RATE:1.0}"
+database:
+  hosts:
+    - "${DB_HOST:localhost}"
+  ports:
+    primary: "${DB_PORT:3306}"
+    replica: "${DB_REPLICA_PORT:3307}"
+`)
+
+var config Config
+err := jenv.UnmarshalYAML(yamlData, &config)
+if err != nil {
+	fmt.Printf("Error: %v\n", err)
+	return
+}
+
+fmt.Printf("Config: %+v\n", config)
+
+```
+
+Ensure you have environment variables set for the tests, or mock them in your test code.
+
+## Contributing
+We welcome contributions! Please follow these steps:
+
+* Fork the repository.
+* Create a feature branch: `git checkout -b feature-name`.
+* Commit your changes: `git commit -m "Add feature"`.
+* Push to the branch: `git push origin feature-name`.
+* Open a Pull Request.