Set Rust toolchain to 1.41.1

The project does not compile on 1.34.0 because it uses
the lockfile format introduced in 1.38.0.

Do note that Debian stable at this time uses Rust 1.41.1.

Setting a specific toolchain version is good practice for
binary project and remove potential issues of incompatible
toolchain for users trying to build the project.

.github/workflows/rust.yml

@@ -3,11 +3,16 @@ name: Rust
 on: [push, pull_request]
 
 jobs:
-  build:
 
     runs-on: ubuntu-latest
 
     steps:
+      - name: Install Rust
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: ${{ matrix.toolchain }}
+          profile: minimal
+          override: true
       - uses: actions/checkout@v1
       - name: Check
         run: cargo check

Cargo.toml

@@ -18,9 +18,6 @@ spec = "config_spec.toml"
 [profile.release]
 lto = true
 
-[features]
-latest_rust = []  # use latest Rust features (otherwise, support Rust 1.34)
-
 [dependencies]
 base64 = "0.10"
 bincode = "1.0"

doc/usage.md

@@ -4,7 +4,7 @@
 
 ### Build dependencies
 
-Install [recent Rust](https://rustup.rs/) (1.34+, `apt install cargo` is preferred for Debian 10),
+Install [recent Rust](https://rustup.rs/) (1.41.1+, `apt install cargo` is preferred for Debian 10),
 [latest Bitcoin Core](https://bitcoincore.org/en/download/) (0.16+)
 and [latest Electrum wallet](https://electrum.org/#download) (3.3+).
 

rust-toolchain

@@ -0,0 +1 @@
+1.41.1