Add Infura API key env var intructions

.gitignore

@@ -37,6 +37,7 @@ target/
 
 # END AUTOGENERATED
 
+.env
 cairo1
 cairo2
 starknet-venv/

README.md

@@ -63,6 +63,14 @@ $ make build
 ```
 Check the [Makefile](/Makefile) for additional targets.
 
+#### RPC State Reader
+
+In order to use the RPC state reader add an Infura API key in a `.env` file at root:
+
+```
+INFURA_API_KEY={some_key}
+```
+
 #### How to manually install the script dependencies
 
 `cairo-lang` requires the `gmp` library to build.
@@ -94,6 +102,8 @@ You can find an example on how to use the CLI [here](/docs/CLI_USAGE_EXAMPLE.md)
 
 ### Testing
 
+[Add an Infura API key.](#rpc-state-reader)
+
 Run the following command:
 ```bash
 $ make test

rpc_state_reader/Cargo.toml

@@ -18,3 +18,4 @@ cairo-lang-starknet = "2.1.0-rc2"
 starknet = { workspace = true }
 thiserror = { workspace = true }
 serde_with = "3.0.0"
+dotenv = "0.15.0"

rpc_state_reader/src/lib.rs

@@ -1,4 +1,5 @@
 use core::fmt;
+use dotenv::dotenv;
 use serde::{Deserialize, Deserializer};
 use serde_json::json;
 use serde_with::{serde_as, DeserializeAs};
@@ -106,6 +107,9 @@ struct RpcResponseFelt252 {
 
 impl RpcState {
     pub fn new(chain: RpcChain, block: BlockValue) -> Self {
+        if env::var("INFURA_API_KEY").is_err() {
+            dotenv().expect("Missing .env file");
+        }
         Self {
             chain,
             api_key: env::var("INFURA_API_KEY")