NGINX:如何使用从nginx.conf到Nginx C语言的设置变量策略？

set $my_var "Hello, World!";

location / {
    proxy_pass http://$my_var;
}

#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_http.h>

static ngx_int_t ngx_http_my_module_variable(ngx_http_request_t *r, ngx_http_variable_value_t *v, uintptr_t data) {
    v->len = sizeof("Hello, World!") - 1;
    v->data = (u_char *) "Hello, World!";
    v->valid = 1;
    v->no_cacheable = 0;
    v->not_found = 0;
    
    return NGX_OK;
}

static ngx_http_variable_t ngx_http_my_module_variables[] = {
    { ngx_string("my_var"), NULL, ngx_http_my_module_variable, 0, NGX_HTTP_VAR_CHANGEABLE, 0 },
    { ngx_null_string, NULL, NULL, 0, 0, 0 }
};

static ngx_int_t ngx_http_my_module_init(ngx_conf_t *cf) {
    ngx_http_variable_t *var, *v;

    for (v = ngx_http_my_module_variables; v->name.len; v++) {
        var = ngx_http_add_variable(cf, &v->name, v->flags);
        if (var == NULL) {
            return NGX_ERROR;
        }

        var->get_handler = v->get_handler;
        var->data = v->data;
    }

    return NGX_OK;
}

static ngx_http_module_t ngx_http_my_module_ctx = {
    NULL,                                  /* preconfiguration */
    ngx_http_my_module_init,               /* postconfiguration */
    NULL,                                  /* create main configuration */
    NULL,                                  /* init main configuration */
    NULL,                                  /* create server configuration */
    NULL,                                  /* merge server configuration */
    NULL,                                  /* create location configuration */
    NULL                                   /* merge location configuration */
};

ngx_module_t ngx_http_my_module = {
    NGX_MODULE_V1,
    &ngx_http_my_module_ctx,               /* module context */
    ngx_http_my_module_variables,          /* module directives */
    NGX_HTTP_MODULE,                       /* module type */
    NULL,                                  /* init master */
    NULL,                                  /* init module */
    NULL,                                  /* init process */
    NULL,                                  /* init thread */
    NULL,                                  /* exit thread */
    NULL,                                  /* exit process */
    NULL,                                  /* exit master */
    NGX_MODULE_V1_PADDING
};