Add rust to go dynamic library example.

rust-to-go-dynamic/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "rust-to-go"
+version = "0.1.0"
+authors = ["Andrey Voronkov <voronkovaa@gmail.com>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+libc = "0.2"

rust-to-go-dynamic/build.rs

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+use std::process::Command;
+
+fn main() {
+    println!(r"cargo:rustc-link-search=target/debug");
+    let os = Command::new("uname")
+        .output().unwrap();
+    let ext = match String::from_utf8_lossy(os.stdout.as_slice()).into_owned().trim_end().as_ref() {
+        "Darwin" => "dylib",
+        _ => "so"
+    };
+    Command::new("go").args(&["build", "-o", &format!("target/debug/libdouble_input.{}", ext), "-buildmode=c-shared", "src/double.go"])
+        .status().unwrap();
+}

rust-to-go-dynamic/src/double.go

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+package main
+
+import "C"
+
+//export DoubleInput
+func DoubleInput(input int32) int32 {
+  return input * 2
+}
+
+func main() {}

rust-to-go-dynamic/src/main.rs

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+extern crate libc;
+
+#[link(name = "double_input")]
+extern {
+    fn DoubleInput(input: libc::c_int) -> libc::c_int;
+}
+
+fn main() {
+    let input = 2;
+    let output = unsafe { DoubleInput(input) };
+    println!("{} * 2 = {}", input, output);
+}